FRONTAL LOBES CONTRIBUTION TO CONSCIENCE, AS A RATIONAL/NON-RATIONAL JUDGMENT SELECTION FILTER
Rationale: The Frontal Lobes (FLs) represent the highest level of brain develop-ment in phylogeny (they were the last to develop). Nevertheless, the functions ascribed to them by neurophysiology (working memory, emotion, psycho-motricity) also involve other structures and are not at the top of mental hierarchy. The aim of this work was to find the critical psychic function mediated exclusively by the FLs.
Methods: 35 subjects (10 normal and 25 pathologic) were explored by EEG before and during performance of the tasks implicating rational and non-rational/emotional judgment. The cortical areas involved in these tasks were topographically determined by the functional EEG Spectral Reaction Mapping.
Results: The rational judgement (explored by checking 15 proverbs significance) induced an EEG activation in the left Wernicke area and, typically, in the left lateral dorsal prefrontal area. The non-rational (emotional) judgment (explored by a ten paintings selection) induced an EEG activation in the occipital right parietal areas and more specifically in both basal (orbital) frontal areas. The FLs reaction in the rational task was abolished in subjects having judgment difficulties, while posterior (parietal) association areas remained normally active.
Conclusions: It is concluded that both types of judgment are exclusively mediated by the FLs. Conscience is the superior mental function acting like a filter confronting these two particular selection mechanisms, in order to decide whether an action must, may or deserves to be done. Thus, judgment errors may decisively alter our decisions. In this case the feed-back information about the results of the given action may be re-evaluated by Conscience, either in emotional or in practical terms.
The prefrontal cortex reaches its greatest relative size in humans and does not fully mature until late adolescence (20) (35). A large majority of the scientists dealing with the dilemma of the Frontal Lobes (FLs), the Phineas Cage case, admitted that the frontal cortex represents the highest stage in the cortical hierarchy of areas mediating mental processing. Despite this common acceptance, no single unitary system exists to describe the proper contribution of the FLs in psychic/mental activity. We observed that many of the superior functions attributed to them are shared in common with other significant cerebral structures.
One of the most important functions ascribed to the Frontal Lobes was operative memory. Many authors reported that FL damaged patients have difficulties in sustaining Short-Term (STM) / working memory and that some FL neurons exhibit a persistent firing during the task-imposed delay period (3 – 9) (14) (17). What the majority of these authors neglect is that all the described working memory tasks involve a selection (choice) between multiple goals (solutions), a function which is completely different from STM. One can find in change important STM deficits in man and animals with hippocampal damage (18) (22). Investigating EEG recordings with chronically implanted electrodes in mammals we found, moreover, that the memory traces released by intermittent light stimulation, used as a preparatory (cue) stimulus in a go- no go (approach-avoidance) task, develop exclusively in the cognitive thalamo-cortical circuits (never in Hippocampus). We related the variation of electrical activity in Dorsal Hippocampus (from theta to fast activity) to the opening / closing of specific and unspecific (activator) thalamic pathways (21) (22). Scientists who investigated the clinical consequences of FL lesions tend to put forward the anomalies of psychomotor behavior, separating two canonical syndromes (13) (16). The first, characterized by loss of initiative and a propensity for apathy (emotional blindness) called the frontal abulic syndrome, was associated with the damage of the dorsal-lateral surface of FL. The second, called disinhibitory syndrome and characterized by “too much behavior“(hypomanic behavior) was associated with basal orbital lesions. This description suggests a segregation of FL inhibitory and excitatory functions. Our experimental studies (21) (22) brought convincing evidence that psychomotor behavior is rather integrated once again by the Hippocampus. It is true that both Dorsal and Ventral Hippocampus have anatomical connections with FL areas (19). The dorsal limbic pathway running through the Cingulum goes to the orbital-frontal cortex; the ventral limbic pathway goes through the Extreme Capsule to the dorsal-lateral Frontal cortex. Thus, the frontal abulic and hypomanic syndromes may be not exclusively consequent to FL proper lesions, but the result of this complex relation disruption.
Other symptoms constantly encountered in the FL syndromes consist in emotional changes such as the emotional hyperactivity of patients with orbital-frontal lesions (yet incapable to infer another person’s mental or emotional state) or the lack of emotionality of patients with dorsal FL lesions. The FL areas could modulate the visceral correlates of emotion through their amygdalo – hypothalamic connections (12), which does not mean, once more, that their function is limited to the emotional expression. The contribution of FL areas in human mental activity should surpass this level of automatic/ executive function.
Examining the mental disorders occurring in 100 patients with cortical epileptic foci (24) (28) we drew the conclusion that the constantly affected area of the mind in case of FL damage is Conscience. We defined Conscience as the highest level of the mind, deciding if a given planed action must be, may be or deserves to be done. The complexity of this function supposes the coordination of a multitude of subsequent processes intervening in the way to action, such as judgment, insight and decision making, as well as the existence of some individual reference scales concerning human values (moral, social, ideal). We described three psychopathologic syndromes in FL epileptics: a) anxious, paranoid, compulsive, antisocial in case of orbital basal foci; b) agitated, hypomanic, with cognitive disorders in case of sagittal foci; c) perseverating and confused in case of dorsal – lateral foci.
The goal of this paper is to further check the relations between mind/conscience and the FL cortex. We intended to find adequate ways for testing exclusively the above supposed rational and non-rational types of judgment, by tasks not involving memory or psychomotor correlates, in order to demonstrate that they are mediated exclusively by the FLs. So, we used EEG Mapping investigation, in normal and pathologic subjects, for detecting the peculiarities of functional activation of the brain.
Subjects: Included in this study were 35 subjects, aged between 18 and 60 years, males and females. Ten of them were normal persons, without antecedents of cerebral pathology, 25 presented various degrees of cerebral pathology, affecting FLs function. All were right handed and had at least 12 years scholarship.
Psychological testing: Our endeavor was meant to find psychological tasks that avoid the working memory paradigm (the delayed A non B task with previous exposure of the situation), as well as the involvement of psychomotor responses.
For the rational type of judgment we utilized a set of 15 proverbs implying some degree of difficulty. E.g.: “Hell is paved with good intentions”. Subjects were asked to give their own interpretation of the proverbs, after ten seconds of thinking. An evaluation of response correctness was done, which was eventually transformed in a global score.
For testing the emotional judgment, based mainly on feelings and personal trends, we employed the presentation of 10 paintings, selected to be different in structure (colors and style).This type of subjective judgment is known since very long time (“Le coeur a des raisons que la raison ignore”). The subject was asked to observe the pictures simultaneously during one minute, and to choose one picture they liked and one picture they detested. The task could give some rough information about the personality trends of the subject.
Electrophysiological investigation: Our study of cerebral electrical activity was performed using an EEG investigation on 19 channels (the 10-20 International System), with left ear reference (electrodes impedance round 5 K Ohms). Subjects were comfortably laid on a sofa, in a quiet environment. The EEG recording was performed first at rest, with the eyes closed, during 3 minutes. In the second stage a similar EEG recording was performed during one of the two described tasks (proverbs hearing with the eyes closed, painting inspection with the eyes open). The EEG recording was stopped before asking the subject a response to the given task.
All subsequent mathematical processing was done using a Pentium PC and our own program of EEG Mapping (26) (27). This software package includes a lot of changes which allow the creation of very characteristic EEG Maps, both in resting conditions and on application of the tests. The main improvement we inserted in our EEG processing system was the “Source Derivation Filtering“. The greatest problem in the EEG Mapping of monopolar recordings is the overwhelming contamination of EEG tracings due to horizontal current diffusion. The total current energy in a biological tissue is of two kinds: 1) the primary, active current, induced by the ionic flow between intra and extra-cellular spaces, 2) the volume (passive) current, representing the dynamic response of the media. Only 10% of this current penetrates directly the scalp; 90% of it suffers a horizontal diffusion. Our procedure for the elimination of volume conducted currents (debluring) was based on an autoregressive model. From the electrical activity power of each source, calculated after Fourier analysis, we extracted the weighted mean power of the 4-5 nearest electrical sources. Once this contamination is excluded, one can find the true local power magnitude. Our results demonstrated the good resolution of such an investigation. Each source cumulates the surface cortical activity in the source and the deep electrical activity of the brain, projected to the surface on a vertical/radial vector. A supplementary facility of this program permits a full artifact rejection. The transformation obtained in the EEG tracings by this procedure is presented in Fig 1.
Fig 1: Effects of Source Derivation Filtering on the topographic differentiation of EEG rhythms. The recording is presented before and after filtration. This procedure improves the resolution of the EEG Power Mapping (at rest or on stimulation), as well as the Evoked Potentials
Mapping quality. Calibration: Amplitude 50 uv/ cm; Time Constant 0.3, Low pass filter 70 Hz. Sampling rate: 256 Hz.
These digitized EEG tracings are further used by the program, which performs the power interpolation and EEG Mapping. Frequency band power maps and various coefficients of power values can be plotted. Among the last, we preferably use the Delta-Theta/Alpha-Beta ratio, paradoxically relevant both in case of EEG abnormality (at rest) and of normal functional activation.
Many other improvements were added in time in this Mapping program. Among them the use of stable (progressive) power scales, making possible an easy comparison between different maps, either transversally (between different subjects) or longitudinally (in the same subject, at various intervals of time).
The second step in this investigation consisted in a “functional” EEG Mapping procedure (25) (30) that we called the “Spectral Reaction Mapping” (SRM). Performing EEG power evaluations in different conditions (% power on stimulation/rest), one can observe and localize the effects of a given functional task on the EEG activity. The procedure was successfully performed in order to evidence the cerebral effects of visual, auditory, verbal, motor, lexical stimulation and so on (29) (32). In this study we use SRM to assess the cerebral electrical activity changes induced by mental judgment testing. Changes in EEG power are appreciated per cent; two available reference scales (one up to 550 %, the second up to 275 % on 11 steps). measuring reaction intensity. On these scales the percentage of 100 % (colored in blue) indicates the topographic cortical areas characterized by no EEG change. Increases in these percentages (colored in green, yellow, orange, red) indicate the enhancement in power of a given cerebral electrical activity (delta, theta, alpha, beta), or of a power ratio, during the imposed psychological testing. Statistical analysis was further made by plotting grand average (group) Maps, or t-significance Maps.
a) EEG Mapping normal reactions on judgment capacity testing.
Fig 2 presents two Group Average Maps obtained by summating the EEG effects of rational and non-rational (emotional) judgment in 10 normal subjects. These are Spectral Reaction Maps (testing versus rest power ratio mapping). One can easily observe the difference between the two functional patterns.
GROUP MAPPING 4788 I.I (m, 40ys)
Fig 2. EEG Spectral Reaction Mapping in rational (proverbs) and emotional w (painting) judgment. On the left: group Maps, on the right an individual Map.
The rational (logic) judgement, which is verbal (listening and interpretation of 15 standard proverbs) involves mainly the left hemisphere. One should mention that on Grand average Maps the EEG changes may be less strictly delimited. Still, on the Map the left parietal Wernicke area is visibly activated. The EEG activation consists in an increase of the Delta-Theta /Alpha-Beta power ratio of 225%. It surely results from the efforts to understand the proverb statements received by the subject. Then, there is a propagation of excitation, and a 175% average activation of the left dorsal prefrontal area, where the solution selection must be performed, occurs. In this case Broca area is not involved, because recordings are taken in the preresponse period.
The non-rational (emotional) judgment was based on visual choice between 10 paintings of preferred and rejected images. EEG activation in this situation involves mainly the right hemisphere. One can see a bilateral activation of the occipital lobes, then its propagation to a right central parietal area (meaning understanding} and to both lateral frontal lobes.
The image of emotional EEG activation obtained in a single highly responsive subject allows a better understanding of the process. The difficulty for common people lies in the two-dimensional representation of the map. We must keep in mind the brain volume, the deep structures probably involved and the inflow direction. It can be observed that, in case of paintings choice, the primary activation is “attracted” in the right occipital-parietal area. The next mysterious fact is the bifurcation of excited pathways, possibly sub-cortical, from a mid line (through Dorsal Median Thalamic nucleus peduncles) to both hemispheres. Finally, we consider orbital the activation of the extreme lateral FL areas. Taking account of the fact that Source Derivation reveals radial vectors of deep generators, this activation in the pF1-F7 and pF2-F8 region must reflect the functional status of the basal/orbital Frontal areas.
One may also observe in this image the opposite EEG reaction of the left dorsal Frontal lobe area (mediating rational judgment) characterized by a decrease in the Delta-Theta/Alpha-Beta ratio, to that of the Frontal orbital areas (mediating emotional judgment), possibly suggesting their functional antagonism.
It is possible that each of the two basal-lateral frontal areas has its specific contribution in the inner acceptation or rejection of the given pictures. The FL contribution in both types of judgment investigated is obvious on these images, although no planning and no motor response is performed.
The sharp functional delimitation of the two hemispheres demonstrates the good resolution of our EEG Mapping procedure.
b) Pathological responses demonstrated by EEG Mapping in rational judgment testing.
In Fig.3, individual responses to the proverb interpretation task and the effects of pathology on the corresponding Spectral Reaction EEG images are illustrated. The idea was to find whether FL function and judgment are connected.
Fig.3: EEG Mapping of rational Judgment Testing (proverbs interpretation) in pathological conditions. Cases: R.M – head-aches; .D.G. – extirpated left FL tumor; V M. and S.A – Epilepsy. For explanations see text.
Subject R.M. (male, 36 years) although complaining of headaches, for which he was addressed, succeeded to give a significant number of correct responses in proverbs testing (80%). His EEG Mapping at rest shows a diffuse slight increase of Delta-Theta / Alpha-Beta power ratio (0.4-2). The map obtained during testing shows instead a clear-cut normal activation of the left Wernicke, propagated to the left prefrontal area. The Spectral Reaction Map demonstrates the strong increase (275 %) of the ratio in the left parietal and prefrontal cortex, on testing versus rest.
Subject D.G. (male, 60years), suffered 6 years earlier the surgical removal of a left FL tumor. He presented since three grand mal seizures, but his neurological status was considered to be normal. The EEG Mapping at rest reveals a severe spontaneous abnormality of the left FL area activity (Delta partial power up to 45%), that persisted during proverbs testing. His task performance was overtly low (10%). The Spectral Reaction Mapping (Testing versus Rest EEG powers comparison) reveals a remarkable compensating activation of the right hemisphere, which involves not only the right prefrontal area (200%) but also the right parietal area (200%). This evident functional transfer could not compensate, however, the psychological deficit of rational judgment manifested by this patient.
Subject V.M. (male, 47 years) was an epileptic presenting approximately two tonic clonic seizures per month (treated with Phenobarbital and Carbamazepine). His EEG Mapping at rest is not seriously affected (Delta Theta / Alpha Beta ratio: 0.4-1.2). He reported Short Term Memory deficits, but had also an extremely poor performance on the proverbs interpretation task (0%). When asked to answer, he repeated obstinately the proverbs “ad literam”. The EEG Spectral Reaction Mapping shows a correct activation of the left Wernicke area (200%), but totally absent electrical activation of the dorsal FLs (100%, i.e. no EEG response on testing versus rest). One can see, instead, an abnormally high activation of the right temporal lobe zone (150-200%).
Subject S.A. (female, 46 years) also reported spells since several years, this time accompanied by manifestations of vegetative character: gastric pain, suffocation, associated with anxiety, eventually fainting (without convulsions).His performance in the proverb interpretation task was of only 40%. His EEG Mapping image at rest looks normal (Delta-Theta /Alpha-Beta ratio: 0.4-1.2). On the judgment testing the Spectral Reaction Map shows a strong activation of the left Wernicke area (275%) but sensory inflow deviation from its normal course to the left dorsal prefrontal area to the lateral-basal (orbital) area of the left FL In such cases we ordinarily suppose the existence of a focal hyper-excitability (31), which is at the origin of the generated spells. The abnormal excitability (common in epileptics) creates in this case an attraction of the normal flux of information during judgement to basal FL areas. One may presume that in such conditions judgment becomes prevalently emotional, which explains the diminished rational performance score of our patient.
These cases denote the complexity of mental activity disorders occurring in pathology, but also the possibility to better understand them by EEG Mapping.
Thus, the suppositions formulated in the introduction are confirmed: 1. Judgment is of two types, which are both mediated exclusively by FL structures. The first expresses the objective reason, the second a subjective reason. 2. FL structures are activated by such mental processes, independently of STM or Drive correlates.
The value of EEG Mapping. This technology is extremely efficient in the detection of cerebral activity. Why then, is it so rarely used to demonstrate functional processes developing in the brain, and MRI (SPECT, PET) is preferred? (9) (14) (34). The neuronal assembly electrical activity is much more proximal to function (or even a functional expression of neuronal activity) than blood flow changes or glucose consumption. Moreover, those imagistic methods can not unveil the dynamics of cortical activation, nor can they answer the question of sequential versus parallel activation, of feedback or feed-forward processes. Our long lasting experience showed that EEG recording in the 10-20 International system and power interpolation may give sufficiently reliable/accurate results, an increased number of recording electrodes being not necessary (they enhance currents interference).The imagistic value of this method is attested by the present study. Spectral Reaction Mapping was a good tool for defining functional EEG changes showing the areas of maximal involvement in the mental process, their interrelationship and their functional failure in case of cerebral pathology. We could distinguish the functional mechanisms involved in the two types of choice (judgment) by which an individual, exposed to various life demands, adapts his behavior. In a comparable study effectuated on a Go- No-Go task by Babiloni et al. (1) with a high resolution EEG (46 channels) and surface Laplacian estimation, the EEG Mapping images obtained were less relevant.
The changes we found are, additionally, specific. In a previous work (30), studying the imagistic effects of the verbal function, we utilized a set of simple sentences that the subjects had to “repeat” after a short period of time. The EEG Spectral Reaction Mapping evidenced then a very impressive activation of left Broca area (in dextrals), and not the activation of the dorsal prefrontal area. This fact sustains the assumption that the prefrontal granular cortex is specifically involved in the rational judgment mechanisms.
Role of the FLs in mental activity
In our opinion Conscience uses these two types of judgment in order to decide that a given action must, may or deserves to be done. There are several brain structures which prepare action (the coordinated activation of the motor centers) in response to a life demand. In straight cooperation, the FL centers decide “what” has to be done, the limbic structures (Hippocampus, as generator of psychomotor initiative) “when”, and the Parietal associative areas (site of intellectual activity) “how” an action must be done. A feedback, expressing the impact (good or bad) of our deeds in the outside world, returns and is also processed by the FLs, and also contributes to Conscience. Shakespeare complains what happens when an individual (Hamlet) has too much rational conscience: “Thus, conscience does make cowards of us all”… Generally, we are confronted in fact with a diminished rational conscience, due either to an evident damage of the FLs, or to their incomplete maturation (they maturate towards 21 years), and with a rigid, inflexible type of conscience, manifested by the overwhelming predominance of the irrational (emotional) type of response. According to Messulam (16): “the socially appropriate comportment and moral conduct are dependent on the ability to transcend an egocentric point of view“, in other words, to pass from the unique emotional judgment, to rational judgment.
Our experiments showed that the two types of selection/choice, decision making, are sub-served by distinct FL areas. These areas activation, demonstrated by EEG Mapping, occurs even in conditions of less working memory or evident motor initiation, when subjects are asked to find the solution of a puzzle. When this puzzle consisted in a proverb interpretation, the EEG activation consisted, on Spectral Reaction Mapping, in a Delta-Theta / Alpha-Beta ratio enhancement in the projection area of the dorsal prefrontal cortex. The emotional/ffective judgment (paintings choice) induced the same ratio enhancement in the projection areas of both FLs orbital cortex. So, it seems that both types of judgment are normal, and may be both disturbed in pathologic conditions. Although the two types of judgment/conscience are opposite, they seem to contribute both to the human mind excellence. The rational conscience performs a better analysis of the situation to be resolved. The emotional conscience stimulates imagination, and the evolution of the arts.
When the left prefrontal cortex was damaged by a tumor (case D.G.), the normal left EEG reaction to proverbs interpretation was absent, and the test performance was concomitantly low, in spite of the appearance of a compensatory activation in the right prefrontal area. In another work (15), testing the Spectral Reaction to classical music (in a musically trained subject) by EEG Mapping, we found a characteristic activation in the right prefrontal area, in association with strong alpha synchrony in the left, a fact which denotes the specialization of these FL areas in relation with verbal, non-verbal functions. In patients with Epilepsy (V.M. and S.A) the increased excitability of the epileptic foci (either temporal or frontal-orbital) may induce a deviation of functional activation from the left prefrontal area; in such conditions the response of the dorsal FL area was considerably reduced, and the performance in proverb testing diminished, although the activation of the left posterior (parietal) association field continued to be strong. This may explain the “dilemma” regarding the destruction of the FLs: the intact persistence of cognition and intelligence. The functional disorders in FL patients disturb only judgment and conscience.
Scientists analyzing the FL syndrome (13) (16) (24) (28), described a profusion of psychological deficits, both in case of dorsal prefrontal and in case of basal, orbital cortex damage. They all stem from the ignored disturbance of the same original judgment mechanisms. Thus, it was demonstrated that patients with dorso-lateral prefrontal cortical damage become puerile, slovenly, facetious, irresponsible, incapable of abstract reasoning, problem solving, sequential behavior, creativity, unable to grasp the context in a complex situation, may loose insight and foresight. Patients with basal, orbital FL cortex damage presented judgment disorders too. Our investigation in epileptics showed that the psycho-pathologic process is complex in this case, because damage or deficit in one FL basal area may induce a hyper-activation on the opposite side (32). At rest, when Delta activity prevails in one orbital area, Beta partial power may be enhanced in the opposite sibling one. Panic attacks occur in some cases, in younger subjects ADHD. The described symptomatology may result from a mixture of deficit and increased irritability causes. These patients also loose mental flexibility, their behavior becomes compulsive, stereotyped, egocentric, they often manifest delusions (of guilt or pursuit), have a tendency to fanaticism, they do not understand social constraints, are able to aggression (even murder), their behavior is often considered psychopathic or sociopathic. In our experience, patients with sagittal foci (on the internal face of the hemispheres) were those who became agitated (hypomanic), had “grandeur” delusions and cognitive disorders (26).
The attempt of Damassio (5) to ascribe morality to the FLs function is not satisfactory; morality is not a brain function, but a reference behavioral scale, different from an individual to another. Moreover, the FL mechanisms do not decide only about ethic issues (right and wrong), but also about esthetic (beautiful-awful), axiological (value-non-value), cognitive (true-false), about forecast (good-bad) and practical issues (useful-useless). Judgment is a brain function and disposes of specific cortical areas and of distinct FL mechanisms. The differences between the two types of judgment may depend on the particular cyto-architectonics of the involved FL regions (7) (19) (20). The prefrontal dorsolateral area is one of the latest achievements in brain development; it is a neo-neocortical area. The structure of this exclusively granular associative cortex is particular, presenting a tendency to loose columnar organization. Neurons are disposed in six layers, successive connections being formed (each neuron sends connections to other 5000 neurons). This particular arrangement can sustain, in our opinion, a heuristic type of judgment: gradual binary yes/no selection of the solution, by progressive, more and more refined steps (like in chess playing). Therefore, this type of judgment is slow and accompanied by doubt. The orbital FL cortex is much more primitive. It is non-granular or dys-granular, has only three layers with lower cellular density, strong afferent connections with emotional (motivational) centers like the amygdala and the hypothalamus, a pyramidal layer and strong efferent connections with the supplementary motor area from g. Cinguli. It has also some great size cells which are implicated in a special type of memory (in our opinion the memory of ideas accumulated during life, either by education or by personal experience). When decision taking is performed by these areas, it has a possible “algorithmic” mechanism, based on innate (ideals, desires) or acquired algorithms (faith, ideology). This type of judgment is strongly motivated, prompt, and has a high degree of certitude. Of course, these types of judgment have both drawbacks and respective qualities.
We believe that this approach of FLs function is favorable to further research of brain-mind interaction. A large amount of scientific works on the matter occurs presently (2) (5) (10). If the basic mechanisms of judgment, be it rational (logic) or irrational, can be studied in an imagistic way (either by Electroencephalography or by Magnetic Resonance), these procedures could be useful in a lot of mental diseases, from ADHD to Schizophrenia.
Bibliografie / Bibliography
- Babiloni C, Babiloni F, Cappa sf, cicotti F, Del Percio C, Maniusi C, Moretti ov, Rossi s, Sosta K, Rossini pm (2004): Human cortical responses during one-bit short-term memory. A high resolution EEG study on delayed choice reaction time-tasks. Clin. Neurophysiol., 2004, 115, 161-170.
- Bechara A (2005): Decision making, impulse control and loss of willpower to resist drugs. Nature, 8, 1458-1263.
- Chao LL, Knight RT (1998): Contribution of human prefrontal cortex to delay performance. J. Cogn. Neurosci., 10, 167-177.
- Cohen jd, peristein wh, brauer ts, nystrom lf, noll dc, jonides j, smith ee (1997): Temporal dynamics of brain activation during a working memory task. Nature, 386, 604-606.
- Damasio A (2010): Self comes to Mind. Constructing the Conscious Brain. Pantheon Books, New York.
- D’esposito M, Detre JA, Alsop DE, Shin RK, Atlas S, Rossman M (1995): The neural basis of the central executive system of working memory. Nature, 378, 273-281.
- Del Arco A, Mora F (2009): Neurotransmitters and prefrontal cortex – limbic system interactions. Implications for plasticity and psychiatric disorders. J. Neurol. Transm., 116, 941-952.
- Diamond A, Goldman Rakic PS (1989) : Comparison of human infants and rhesus monkeys on Piaget’s A- not B task: evidence for dependence on dorso- lateral prefrontal cortex. Exp. Brain Res., 74, 24-40.
- Diamond A, O’craven KA, Savoy RI (1998): Dorso-lateral prefrontal cortex contribution to working memory and inhibition as revealed by f MRI. Society for Neuroscience. Abstracts, 24, 1251.
- Ernst LU, Pichta MM, Lutz E, et all (2013): Prefrontal activation patterns of automatic and regulated approach-avoidance reactions. A functional near infrared spectroscopy study. Neuropsychologia, 48, 131.
- Fuster JM, Alexander GE (1971): Neuron activity related to short-term memory. Science, 193, 652-654.
- Goldman PS, Rosvold HE, Vest B, Balkin TW (1971): Analysis of the delayed –alternation deficit produced by dorso-lateral prefrontal lesions in the rhesus monkey. J. of Comp. Physiol. Psychiat, 77, 212-220.
- Knight RT, Stuss DT (2002): Prefrontal cortex. The present and the future. In: Principles of Frontal Lobe function. Stuss, D.T.,Knight, RT.(Eds.),Oxford Univ. Press, pp. 8-30.
- La Bar KS, Gitelman DR, Parrish TD, Mesulam MM (1999): Neuroanatomic overlap of working memory and spatial attention networks: a functional f.MRI comparison within subjects. NeuroImage, 10, 695-704.
- Matei M, Psatta DM, Teutsch W (2005): Cerebral processing of music. Rom.J.Neurol. 43, 67-77.
- Messulam MM (2002): The human Frontal Lobes: Transcending the Default Mode through contingent encoding. In: Principles of Frontal Lobe function.. Stuss, D.T.., Knight, RT (Eds). Oxford Univ.Press. pp 8-30.
- Moscovitsch M, Vinocur G (2002): The Frontal cortex and working with memory. In: Principles of Frontal Lobe function. Stuss,D.T.,. Knight R.T. (Eds). Oxford Univ. Press, pp. 188-209.
- Penfield W, Milner B (1958): Memory deficit produced by bilateral lesions in the hippocampal zone. AMA Arch.Neurol.Psychiat, 74, 475-497.
- Petrides M, Pandya DN (2002): Association pathways of the prefrontal cortex and functional observations. In: Principles of Frontal Lobe function. Stuss, D.T., Knight R.T. (Eds). Oxford Univ. Press, pp. 31-50.
- Preuss TM (2000): What’s human about the human brain. In: The new cognitive Neurosciences. Gazzaniga, M.S. (Ed). MIT Press, pp. 1219-1234.
- Psatta DM (1972): EEG patterns of motivation in cats during approach- avoidance successive differentiation. Rev. roum. Neurol., 9, 229-248.
- Psatta DM (1972): EEG patterns of Short Term Memory in cats during approach – avoidance successive differentiation. Rev. roum. Neurol., 9, 244-263.
- Psatta DM (1977): Limbic electrical activity in neurotic cats. Its dependency on the cholinergic – adrenergic ratio. Activitas Nervosa Sup., 19, 124-127.
- Psatta DM (1977): Personality Disorders in Temporal Lobe and Frontal epilepsy. Rev. roum. Neurol. Psychiat., 15, 301-308.
- Psatta DM, Matei M, Burstein G (1988): Deterioration of verbal centers function in aphasics demonstrated by EEG Spectral Reaction Curves. Rev.roum.Neurol.Psychiat, 26, 237-250.
- Psatta DM, Jipescu I, Matei M (1990): A personal computer used for Spectral Power EEG Mapping in Source Derivation. Rev. roum. Neurol. Psichiat.: 28, 79-86.
- Psatta DM, Matei M, Jipescu I (1990): Contribution of EEG Mapping to diagnosis setting in a supratentorial damage. Rev.roum.Neurol.Psichiat. 28, 87-96.
- Psatta DM, Tudorache B, Matei M, Diacicov S: Cerebral (1991) dysfunction revealed by EEG Mapping in the Schizoform Epileptic Psychosis. Rev.roum.Neurol.Psychiat. 29, 81-98.
- Psatta DM, Matei M (1996): EEG Mapping during auditory oddball stimulation; a comparison with P300 scalp distribution in normal controls and epileptic patients. Rom.J.Neurol., 34, 35-53.
- Psatta DM, Matei M (1998): EEG Spectral Reaction Mapping investigation of normal and impaired language function. Rom. J. Neurol., 36, 99-111.
- Psatta DM, Matei M (2001): Centrum ovalae demyelization revealed by EEG Mapping in multiple sclerosis. Rom. J. Neurol., 39, 85-97.
- Psatta DM, Matei M, Apostol M (2002): A new test for detecting EEG focalities in patients with epilepsy: Spectral Reaction Mapping by binocular flash stimulation. Rom.J.Neurol., 40, 3-18.
- Psatta DM, Matei M, Olaru M (2004): Auditory evoked potentials Mapping in Source Derivation. Rom.J.Neurol., 42, 33-45.
- Rowe J, Passingham RE (2001): Working memory for location and time: activity in prefrontal area 46 relates to selection rather than to maintenance in memory. NeuroImage, 14, 77-86.
- Sowell ER, Thompson pm, Holmes CJ, Jernigan TL, Toga AW (1999): In vivo evidence for post adolescent brain maturation in frontal and striatal regions. Nature. Neuroscience, 2, 859-861.
- Szentagothai J (1990): Cascade type reintrance: the major connectivity principle of the neocortex. In: From Neuron to Action. Decke, L., Eccles, J.C., Mountcastle, V.B. (Eds). Springer Verlag, pp 399-406.