Current methodology and methods in psychophysiological studies of creative thinking.

Important points on methodology and detailed description of methods used in polymodal psychophysiological studies of human verbal creative thinking are presented. The psychophysiological studies were conducted with healthy volunteers during implementations of specially developed and adapted psychological tests aimed to bring the subjects into states of verbal creative thinking. Four different task sets ("story composition", "associative chains", "original definitions", "proverb sense flipping") were developed and applied. Positron emission tomography of regional cerebral blood flow (rCBF) and state-related quantitative electroencephalography (power and coherence evaluated) were used. The effectiveness of the methods is illustrated with figures.

Error detection mechanisms of the brain: background and prospects.

Historical background of error detection (ED) studies is restored here from the first suggestion of such a mechanism published (Rabbit, 1966) and the first related anatomo-physiological correlates observed [Bechtereva, N.P., Gretchin, V.B., 1968. Physiological foundations of mental activity. Int. Rev. Neurobiol., vol. 11. Academic Press, N.Y., pp. 239-246; Bechtereva, N.P., 1971. Neurophysiological Aspects of Human Mental Activity. Meditzina, Moskow. 120 pp., (in Russian); Bechtereva, N.P., 1974. Neurophysiological Aspects of Human Mental Activity, second edition, revied and complete Meditzina, Moskow. 151 pp., (in Russian)]. Data from evoked potentials together with new opportunities offered by the technological revolution of the 1980s-1990s provided a large body of knowledge on the ED. The overwhelming majority of the papers stress the spatial relation of ED to Anterior Cingulate Cortex. ED was revealed in a number of other zones to whose role should be specially discussed. The other point of interest is the late appearance of ED after the brain signs of correction which seems particularly important considering the supposed functional role of ED. Data of direct observations of ECoG dynamics in left and right human ACC on correct and erroneous test performance are presented. Research on ED resulted in the development of new ways in treatment of the obsessive-compulsive syndrome. Further psychophysiological research into the ED phenomena is considered as one of the priorities of fundamental and applied investigations for the elucidation of human brain functions. Opinion that ED plays an extremely important role in mechanisms of cognition and creativity is further argumented. Investigations in the field can contribute a lot to clinical neurophysiology as well.

PET study of brain maintenance of verbal creative activity.

This paper deals with the investigation of the brain organization of verbal creativity. Psychological tasks were designed in accordance with two main strategies used by volunteers in solving creative tasks. Regional cerebral blood flow (rCBF) was measured with positron emission tomography (PET) when performing two types of creative tasks in two groups of subjects, each type of the task organizing the creativity process in its own way. Valuable brain correlates of creativity were revealed in the left parieto-temporal regions (Brodmann areas 39 and 40).

Depth electrodes in clinical neurophysiology: neuronal activity and human cognitive function.

Depth intracranial electrodes are used in medicine for the diagnosis and treatment of certain medically intractable disorders including epilepsy and parkinsonism. Electrophysiological studies including the recording of neuronal activity via depth electrodes during cognitive tasks allow the mapping of the functional significance of various brain regions for certain cognitive functions. Knowledge accumulated throughout the last several decades allows us to draw some theoretical inferences about neuronal mechanisms of human cognition. The present paper provides a selective review of studies of neuronal activity of the human brain in relation to language, verbal memory and error detection.

Psychophysiology by the end of the 20th century.

The first real breakthrough in the research of brain organization and thinking in the 20th century was made in neurophysiological investigations performed in direct contact with different sites of the brain, which became possible in diagnosis and treatment. The second breakthrough is happening at present. It is based on the opportunities provided by the non-invasive technique. The theory of the unique character of the brain system consisting of rigid and flexible elements maintaining thinking was created as well as concepts on the reliability in the system, of the error detector and intrinsic protective mechanisms of the brain. In the clinic these data enabled us to help patients who had lost various functions due to stroke. In confirmation with the above theory it was revealed that the same task could be solved in the brain by systems consisting of different elements due to environmental changes or even direction of attention. Data on the functional properties or every zone of the cortex and subcortex as well as cerebellum are rapidly increasing in number. The first priority lies in neurophysiologically penetrating into the physiological character and micromosaic of the activation sites of PET. The main aim of future brain research lies in the investigation of the fine physiological rearrangements which underlie thinking, i.e. deciphering its brain code. This is going to be the basis for the third, extremely valid breakthrough in the research on brain organization of thinking.

Neuronal activity of human caudate nucleus and prefrontal cortex in cognitive tasks.

Lesions of the caudate nucleus and prefrontal cortex may display similar cognitive deficits. Recent advances in cognitive neuroscience have clarified the functional role of prefrontal cortical areas in certain cognitive operations involved in simple language tasks. We have addressed the role of the caudate nucleus in tasks of lexical decision, semantic categorization, recognition memory, reading aloud and object naming by recording neuronal activity in patients with depth electrodes. During visual processing of words, caudate cells exhibited excitatory responses related to both semantic and phonological-articulatory encoding with non-overlapping time courses. The firing rate of the cells was increased when the semantic processing was required. This occurred within 400-600 ms after the stimulus onset, or within the first 200-300 ms of the delay period. The increased firing within 1000-1200 ms after the stimulus onset was related to the phonological processing. These responses turned out to be strikingly similar to those in Broca's area. Both reading aloud and explicit memory retrieval tasks elicited a sustained inhibition of firing of the same cells with a greater onset latency. Chronometric comparison of prefrontal, temporo-parietal and caudate activities in similar tasks relates the time course of these activations to the fronto-caudate anatomical loops and helps further understanding of the anatomy and circuitry involved in human cognition.

Neuronal correlate of the higher-order semantic code in human prefrontal cortex in language tasks.

Recently, Posner et al. (Science, 1988, 240: 1627-1631) have shown by means of positron-emission tomography (PET) that the highest activation related to the higher-order semantic encoding in language tasks is revealed in the anterior inferior region of the left prefrontal cortex. We had a case where we explored the neuronal activity in this cerebral area in a patient with diagnostic intracerebral electrodes. Neurons of the left cortical areas 10 and 46 exhibited responses related to the processing of semantic and grammatic signs of the presented phrases. Specific responses in neuronal activity of the same cells in other higher-order language tasks, in discrimination of concrete and abstract words, and the absence of significant responses in other relatively simpler language tasks, such as object naming and lexical decision, supports the PET finding on the selective participation of this cerebral area in the higher-order semantic encoding and discovers new neuronal mechanisms of this encoding.

Effect of phenytoin on the human neuronal activity and depth event-related potential in emotional task.

Neuronal activity and depth ERP were recorded from cortical areas and subcortical nuclei of three patients with diagnostic and/or therapeutic intracerebral electrodes while they were performing emotional task before and after phenytoin administration. Phenytoin acted as a bioelectrical modulator, in some cases increasing and in some cases decreasing the mean background neuronal firing level. In some few cases the more specific task-related effect of phenytoin was found as an inversion of the inhibitory response into the excitatory one in trials evoking negative emotions.

Properties of neuronal activity in cortex and subcortical nuclei of the human brain during single-word processing.

Neuronal impulse activity (NIA) in different cortical areas, subcortical nuclei of the thalamus and striopallidum was recorded via depth electrodes in human patients as they performed a visual word recognition task. The properties of neuronal responsiveness were compared across regions. During single-word processing approximately 75-80% of the responsive cortical neurons were characterized by poststimulus inhibition of firing rate; an increased firing rate (i.e., excitatory response) was observed in about 20-25% of the responsive cortical neurons. Among the subcortical nuclei, mainly in the thalamus and striopallidum, more than 90% of the responsive neurons were characterized by poststimulus excitation; less than 10% exhibited poststimulus inhibition of firing rate.

Neuronal activity in frontal speech area 44 of the human cerebral cortex during word recognition.

The activity of neurons was recorded from cortical speech area 44 of human patients with diagnostic and/or therapeutical depth electrodes while they were performing word recognition and object naming tasks. Some cells responded selectively to either semantic or phonological aspects of word processing with the same latency, others responded consecutively to both semantic and phonological features. The present finding provides the first demonstration of neuronal mechanisms in frontal language cortex and evidences that both consecutive and parallel processing of these speech signs occur in neuronal activity of this area.

Neural correlate of mental error detection in the human brain cortex.

The use of long-term intracerebral electrodes combined with advances in stereotaxic neurosurgery and a complex multimethodological approach to brain research has made possible a study of the neurophysiological mechanisms of higher mental functions in the course of diagnosis and/or treatment of some chronic cerebral diseases. Investigations in which both local oxygen tension and neuronal impulse activity were recorded while the patients were performing psychological tasks have revealed selective responses in some neuronal populations of the thalamus and of the striopallidal complex, which occur only during erroneous task performance. So-called 'error detector' neurons were also found in the perirolandic and parietotemporal regions of the human brain cortex.

Neurophysiological correlates of verbal activity in patients with speech disorders of traumatic etiology.

The article deals with the neurophysiological correlates of the pathophysiological mechanisms of brain trauma. Mechanisms of damaged function restoration by means of therapeutic electrostimulations (TES) are also under discussion. Localization of the brain zones involved in the maintenance of speech and their expansion, while TES is shown on the basis of functional testing and registration of different indices of bioelectrical activity.

Cerebral lateralization for language revealed in neuronal responses of the human brain cortex.

Neuronal impulse activity (NIA) of the cortex and subcortical nuclei in the thalamus and striopallidar complex was studied during performance of the word recognition test in patients with long-term intracerebral electrodes implanted for diagnostics and therapy. In NIA of the left hemisphere cortex, endogenous responses were found to prevail in the interval between expositions of two stimuli, whereas NIA of the right cortex exhibited more responses during perception of stimuli. Asymmetry in neuronal responses of subcortical nuclei in the thalamus and striopallidar complex appeared to differ from that observed in the cerebral cortex.

In search of cerebral error detectors.

Multiunit activity was recorded from 124 different subcortical sites in 10 parkinsonian patients bearing gold electrodes for diagnosis and therapy. The patients participated in a visual recognition task in which the stimuli (digits) were presented on a LED-matrix at threshold, the exposure times so chosen that in about half the trials the patient failed to recognize the digit correctly. Peristimulus time histograms (PSTHs) for each neuronal population as well as profiles of reactions for all neuronal populations were calculated and statistically analysed, separately for the cases of correct, incorrect, and non-recognition. There are at least 3 groups of neuronal populations, each associated with one temporally separate neurophysiological process involved in the performance of the psychological recognition task. They can be differentiated by the parameters' 'onset' and 'peak' latency. This in itself suggests that they may be related to different psychological processes involved in the task's performance, the earlier components in feature detection and/or evaluation operations concerning the stimulus; the later components, presumably, in processes related to initiation of the actual response. By scanning the individual PSTHs, we found one neuronal population which might be considered an error detector. This population reacted robustly in the early stages of information processing (100-500 ms post-stimulus) only in the case of non-optimal behavior, suggesting that it might somehow be related to signalling an error.

Psychophysiological micromapping of the human brain.

Neuronal impulse activity (NIA) of cortex and subcortical nuclei of the brain was studied in patients diagnosed and treated with the aid of long-term intracerebral electrodes. A special battery of psychophysiological tests was constructed for study of reflexion of different mental functions in NIA, such as various speech functions, short-term and long-term memory, count and arithmetic operations, emotions. Neuronal populations with the significant responses have been revealed during these testings. First results of psychophysiological mapping of the human brain obtained from NIA data have been presented.

Human thalamic and pallidal neuronal responses to visual stimuli in a threshold recognition task.

Multiunit activity was recorded from 80 different subcortical sites in 9 parkinsonian patients bearing gold electrodes for diagnosis and therapy. The patients participated in a visual recognition task in which the stimuli (digits) were presented on a LED matrix at threshold. The exposure times were so chosen that in about half the trials the patient failed to recognize the digit correctly. Peristimulus time histograms for each neuronal population as well as profiles of reactions for the groups of neuronal populations localized in the N. ventro-lateralis thalami and the globus pallidus, respectively, were analysed statistically, contrasting the cases of correct recognition with those of non-recognition. Different types of response, possibly related to different stages of task performance, were separated: an early type with onset latencies ranging from 80 to 160 msec, two middle types with onset latencies ranging from 200 to 300 msec, and a type characterized by slow shifts in the discharge rate beginning 400-600 msec post stimulus. Most of the significant differences in the discharge rate between qualities of recognition were found in the middle-type responses and in the slow shifts, shorter latencies and larger amplitudes accompanying correct recognition.

Some general physiological principles of the human brain functioning.

Implantation of electrodes into the human brain for diagnosis and therapy of different brain disorders enabled the revelation of some general and specific regularities in the brain functioning which, being properly accounted for, may promote further more efficient brain research with both invasive and non-invasive techniques. This is a discussion of three major principles revealed during comprehensive study of the human brain, including stimulation and recording of the broad range of physiological processes both in a relaxed state and when performing a set of psychological tests. (1) The presence of the flexible links in the cerebral systems subserving complex activity; (2) cerebral restrictive and protective mechanisms; (3) the ability of certain brain areas to respond selectively to the erroneous recognition of a given type of activity--error detection.

Single-trial decomposition: a new approach to the analysis of neuronal reactions during psychological tasks.

Neurophysiological and statistical assumptions underlying conventional procedure of averaging the neuronal responses to sequentially presented stimuli or psychological tasks are critically discussed. A new approach to the analysis of the neuronal evoked reactions is developed based on the decomposition of the single-trial discharge rate patterns into the separate peak-shaped components characterised by the latent periods, amplitudes and durations. It is demonstrated that using only latent period and signs of each component's amplitude is sufficient to detect reliably all the latency intervals where the conventional peristimulus-time histograms reveal significant deviations of the neuronal discharge rate from the mean background level. The approach suggested enables the analysis of the real physiological events within the single trials, obscured by the conventional averaging into the peristimulus-time histogram curve.