Ontogenetic aspects of individual characteristics of functional brain asymmetry in the perception of emotions

Studies have been made on individual variations in perception of speech emotional information by 7-16-year children. Significant differences between subjects from various age groups were found concerning the correct recognition of emotions, the degree of brain asymmetry and domination type. The exactness of emotional recognition increases with age, while the degree of asymmetry becomes lower, the right hemisphere domination becoming more stable in processing of speech emotional information. With age, individual type of asymmetry turns to the specific one, reflecting asymmetry formation during evolution.     

Spectral-spatial characteristics of theta range in the EEG of students with various productivity of performance for visual spatial tasks

Examinees, which consisted of 46 young males, were offered to memorize and recreate a sequence of signals on a computer monitor. These signals were to be recreated in regard to the original sequence and location. Examinees were divided into two groups depending on their degree of approximation of the correct location of the signal sequence. The first group, unlike the second (in contrast to the second one), had a very high rate of accuracy with the least number of mistakes. EEG reading was taken on the examinees prior to completing the test, during the memorization stage and during the completion of task. The EEG reading taken prior to the test and those of the completion of task showed no difference in the range ofteta rhythm for both groups of examinees. However, during the memorization stage, the examinees of the first group, unlike that of the second, showed an increase in the coefficient of proximity in the line of teta rhythm EEG of the right hemisphere of the brain. Three systems of connection with the focuses of activity in the right rear, right center and right front areas of the brain, in which the proximity of teta range of EEG during the memorization stage, were noticeably higher in the group of examines that showed high accuracy during the primary attempts of recreation of the sequence. Since the right hemisphere deals mainly with spatial perception of the information and is more active at processing of nonverbal and stereotyped signals, we suggest that students belonging to different groups employed different strategies of processing of the task during remembering.     

Selection of visual hierarchical stimuli between global and local aspects in men and women

Sex differences in global-local hemispheric selective processing were examined by hierarchical letter presenting in conditions of their perception and comparison. Fifty-six right-handed males and 68 females (aged 17-22 years) participated in the experiment. During interference between global and local aspects of stimuli the mean reaction times for correct global responses was quicker than local responses, and the right hemisphere has been dominated during global selective processing independently from the sex. Sex differences in perception of visual hierarchical stimuli were more pronounced than in comparison condition: men prefer mostly the right-hemispheric global strategy of information processing, but women--the left-hemispheric local one. Dominance of global strategy in men and local strategy in women during visual hierarchical stimuli perception together with no sex differences in correct responses indicates possibility of similar results in cognitive activity by different ways.     

Bilateral Theta-Burst TMS to Influence Global Gestalt Perception

While early and higher visual areas along the ventral visual pathway in the inferotemporal cortex are critical for the recognition of individual objects, the neural representation of human perception of complex global visual scenes remains under debate. Stroke patients with a selective deficit in the perception of a complex global Gestalt with intact recognition of individual objects – a deficit termed simultanagnosia – greatly helped to study this question. Interestingly, simultanagnosia typically results from bilateral lesions of the temporo-parietal junction (TPJ). The present study aimed to verify the relevance of this area for human global Gestalt perception. We applied continuous theta-burst TMS either unilaterally (left or right) or bilateral simultaneously over TPJ. Healthy subjects were presented with hierarchically organized visual stimuli that allowed parametrical degrading of the object at the global level. Identification of the global Gestalt was significantly modulated only for the bilateral TPJ stimulation condition. Our results strengthen the view that global Gestalt perception in the human brain involves TPJ and is co-dependent on both hemispheres.     

Information processing specialization during interference between global and local aspects of visual hierarchical stimuli in men and women

Sex-related differences in global/local hemispheric selective processing were examined by hierarchically presented letters in conditions of their perception and comparison. Fifty-six right-handed men and 68 women (aged 17–22 years) participated in the experiment. During the interference between global and local aspects of stimuli, the mean reaction time for correct global responses was shorter than for local responses, and the right hemisphere dominated during global selective processing independently of sex. Sex-related differences in perception of visual hierarchical stimuli were more pronounced than during their comparison: men preferred the right-hemispheric global strategy of information processing, and women, the left-hemispheric local one. The dominance of the global strategy in men and local strategy in women during visual hierarchical stimuli perception, together with the absence of sex-related differences in correct responses indicates the possibility of obtaining the same efficiency of cognitive activity in different ways.     

Perception of consonant and dissonant chords: changes in the power of the EEG evoked activity

Human perception of dissonant and consonant chords was studied by analyzing brain evoked activity. It was found that the perception of dissonant chords was accompanied by activation of the right frontal lobe, which controls negative emotions. Consonant chords activated the left frontal region, which controls positive emotions.     

Functional brain organization of global and local visual perception: an ERP study

Adult subjects were asked to recognize a hierarchical visual stimulus (a letter) while their attention was drawn to either the global or local level of the stimulus. Event-related potentials (ERP) and psychophysical indices (reaction time and percentage of correct responses) were measured. An analysis of psychophysical indices showed the global level precedence effect, i.e., the increase in a small letter recognition time when this letter is a part of incongruent stimulus. An analysis of ERP components showed level-related (global vs. local) differences in the timing and topography of the brain organization of perceptual processing and regulatory mechanisms of attention. Visual recognition at the local level was accompanied by (1) stronger activation of the visual associative areas (Pz and T6) at the stage of sensory features analysis (P1 ERP component), (2) involvement mainly of inferior temporal cortices of the right hemisphere (T6) at the stage of sensory categorization (P2 ERP component), and (3) involvement of prefrontal cortex of the right hemisphere at the stage of the selection of the relevant features of the target (N2 ERP component). Visual recognition at the global level was accompanied by (1) pronounced involvement of mechanisms of early sensory selection (N1 ERP component), (2) prevailing activation of parietal cortex of the right hemisphere (P4) at the stage of sensory categorization (P2 ERP component) as well as at the stage of the target stimulus identification (P3 ERP component). It is suggested that perception at the global level of the hierarchical stimulus is related primarily to the analysis of the spatial features of the stimulus in the dorsal visual system whereas the perception at the local level primarily involves an analysis of the object-related features in the ventral visual system.     

Rearrangement of the Prefrontal Cortex Neural Activity in Both Hemispheres during Learning

Neuronal activity of both right and left hemispheres of the rat prefrontal brain cortex was recorded in the two-ring maze during animal learning to operate in response to signals. At the beginning of learning, pairwise comparison of neural activity that accompanied correct and incorrect choice of the right and left sides showed significant differences in the left hemisphere and the lack of differences in the right one. With increasing percentage of correct choices during a session of learning, the differences in neuronal responses appeared in the right hemispheres and were reduced in the left one. The opposite trends in rearrangement of the total impulse activity are believed to be related to different roles of hemispheres in the construction of the internal behavioral model.     

Characteristics of the perception and imagination of emotions in patients with focal brain pathology

Voluntary components of the emotion perception were shown to be related to the left hemisphere temporal area in patients with focal lesions of postero-frontal and temporal areas of both hemispheres, whereas the involuntary components required involvement of the right hemisphere temporal area. The voluntary components of the emotion reproduction are associated with involvement of the left hemisphere postero-frontal area, whereas involuntary components of perception are related to work of the right hemisphere postero-frontal area. The data obtained suggest that the voluntary (conscious) recognition and reproduction of emotions are mainly related to the sensory and motor speech centres of the left hemisphere, whereas involuntary those involve symmetrical areas of the opposite hemisphere.     

The fusiform face area is engaged in holistic, not parts-based, representation of faces

Numerous studies with functional magnetic resonance imaging have shown that the fusiform face area (FFA) in the human brain plays a key role in face perception. Recent studies have found that both the featural information of faces (e.g., eyes, nose, and mouth) and the configural information of faces (i.e., spatial relation among features) are encoded in the FFA. However, little is known about whether the featural information is encoded independent of or combined with the configural information in the FFA. Here we used multi-voxel pattern analysis to examine holistic representation of faces in the FFA by correlating spatial patterns of activation with behavioral performance in discriminating face parts with face configurations either present or absent. Behaviorally, the absence of face configurations (versus presence) impaired discrimination of face parts, suggesting a holistic representation in the brain. Neurally, spatial patterns of activation in the FFA were more similar among correct than incorrect trials only when face parts were presented in a veridical face configuration. In contrast, spatial patterns of activation in the occipital face area, as well as the object-selective lateral occipital complex, were more similar among correct than incorrect trials regardless of the presence of veridical face configurations. This finding suggests that in the FFA faces are represented not on the basis of individual parts but in terms of the whole that emerges from the parts.     

Neural Bases for Individual Differences in the Subjective Experience of Short Durations (Less than 2 Seconds)

The current research was designed to establish whether individual differences in timing performance predict neural activation in the areas that subserve the perception of short durations ranging between 400 and 1600 milliseconds. Seventeen participants completed both a temporal bisection task and a control task, in a mixed fMRI design. In keeping with previous research, there was increased activation in a network of regions typically active during time perception including the right supplementary motor area (SMA) and right pre-SMA and basal ganglia (including the putamen and right pallidum). Furthermore, correlations between neural activity in the right inferior frontal gyrus and SMA and timing performance corroborate the results of a recent meta-analysis and are further evidence that the SMA forms part of a neural clock that is responsible for the accumulation of temporal information. Specifically, subjective lengthening of the perceived duration were associated with increased activation in both the right SMA (and right pre-SMA) and right inferior frontal gyrus.     

Psychophysiological and neurophysiological features of the organization of visuo-spatial performance in right-handed and left-handed six- to seven-year-old children

The developmental features of individual components of the visual perception and brain functional organization during visuo-spatial activity of different complexity were studied in right-handed and left-handed 6–7-year-old children. The results of psychophysiological testing of their visual perception testify to the underdevelopment of the mechanisms of integrative brain activity. Some specific features of the brain functional organization were revealed in the left-handed children during visuo-spatial performance. More autonomous functioning of the cerebral hemispheres and the duplication of the activation processes in the right and left hemisphere during visuo-spaital performance of different complexity are characteristic of these children. This is probably associated with the involvement of compensatory mechanisms, which enable the performance reliability.     

How Listeners Weight Acoustic Cues to Intonational Phrase Boundaries

The presence of an intonational phrase boundary is often marked by three major acoustic cues: pause, final lengthening, and pitch reset. The present study investigates how these three acoustic cues are weighted in the perception of intonational phrase boundaries in two experiments. Sentences that contained two intonational phrases with a critical boundary between them were used as the experimental stimuli. The roles of the three acoustic cues at the critical boundary were manipulated in five conditions. The first condition featured none of the acoustic cues. The following three conditions featured only one cue each: pause, final lengthening, and pitch reset, respectively. The fifth condition featured both pause duration and pre-final lengthening. A baseline condition was also included in which all three acoustic cues were preserved intact. Listeners were asked to detect the presence of the critical boundaries in Experiment 1 and judge the strength of the critical boundaries in Experiment 2. The results of both experiments showed that listeners used all three acoustic cues in the perception of prosodic boundaries. More importantly, these acoustic cues were weighted differently across the two experiments: Pause was a more powerful perceptual cue than both final lengthening and pitch reset, with the latter two cues perceptually equivalent; the effect of pause and the effects of the other two acoustic cues were not additive. These results suggest that the weighting of acoustic cues contributes significantly to the perceptual differences of intonational phrase boundary.     

Sex differences of functional lateralization in the perception of verbal and emotional information in ontogeny

Experimental data show certain differences between men and women in perception of verbal and emotional information. They are revealed in the ability of correct perception of definite kind of information, in the degree of brain functional asymmetry in perception of the given information, in prevalence of domination type. The character of sex differences in functional asymmetry changes little with the age; quantitative correlations of the coefficient of asymmetry diminish with the age.     

Role of the Right- and Left-Hemispheric Structures in Speech and Memory Formation in Children

The role of structures of the left and right cerebral hemispheres in formation of speech function and memory was studied on the basis of complex examination of children with developmental speech disorders. On the basis of EEG estimation of the functional state of the brain, children were classified in two groups depending on the side of localization of changes in electrical activity: those with local changes in electrical activity in the left hemisphere (group I) and those with changes in the right hemisphere (group II). The medical history suggested that the observed features of topography of local changes in electrical activity were linked with the character of prenatal and labor complications and their consequences leading to embryo- and ontogenetic disorders in development of different brain regions. Comparison of the results of neuropsychological examination of the two groups showed that different regions of the brain cortex of both the left and right hemispheres are involved in speech formation. However, a specific role of the right hemisphere in formation and actualization of automatic speech series was revealed. It was suggested that the integrity of gnostic functions of the right hemisphere and, primarily, the spatial organization of perception and movements is a necessary factor of development of auditory–speech and nominative memory.     

Role of Medio-Dorsal Frontal and Posterior Parietal Neurons during Auditory Detection Performance in Rats

To further characterize the role of frontal and parietal cortices in rat cognition, we recorded action potentials simultaneously from multiple sites in the medio-dorsal frontal cortex and posterior parietal cortex of rats while they performed a two-choice auditory detection task. We quantified neural correlates of task performance, including response movements, perception of a target tone, and the differentiation between stimuli with distinct features (different pitches or durations). A minority of units—15% in frontal cortex, 23% in parietal cortex—significantly distinguished hit trials (successful detections, response movement to the right) from correct rejection trials (correct leftward response to the absence of the target tone). Estimating the contribution of movement-related activity to these responses suggested that more than half of these units were likely signaling correct perception of the auditory target, rather than merely movement direction. In addition, we found a smaller and mostly not overlapping population of units that differentiated stimuli based on task-irrelevant details. The detection-related spiking responses we observed suggest that correlates of perception in the rat are sparsely represented among neurons in the rat''s frontal-parietal network, without being concentrated preferentially in frontal or parietal areas.     

The Right Planum Temporale Is Involved in Stimulus-Driven,Auditory Attention – Evidence from Transcranial Magnetic Stimulation

It is well known that the planum temporale (PT) area in the posterior temporal lobe carries out spectro-temporal analysis of auditory stimuli, which is crucial for speech, for example. There are suggestions that the PT is also involved in auditory attention, specifically in the discrimination and selection of stimuli from the left and right ear. However, direct evidence is missing so far. To examine the role of the PT in auditory attention we asked fourteen participants to complete the Bergen Dichotic Listening Test. In this test two different consonant-vowel syllables (e.g., “ba” and “da”) are presented simultaneously, one to each ear, and participants are asked to verbally report the syllable they heard best or most clearly. Thus attentional selection of a syllable is stimulus-driven. Each participant completed the test three times: after their left and right PT (located with anatomical brain scans) had been stimulated with repetitive transcranial magnetic stimulation (rTMS), which transiently interferes with normal brain functioning in the stimulated sites, and after sham stimulation, where participants were led to believe they had been stimulated but no rTMS was applied (control). After sham stimulation the typical right ear advantage emerged, that is, participants reported relatively more right than left ear syllables, reflecting a left-hemispheric dominance for language. rTMS over the right but not left PT significantly reduced the right ear advantage. This was the result of participants reporting more left and fewer right ear syllables after right PT stimulation, suggesting there was a leftward shift in stimulus selection. Taken together, our findings point to a new function of the PT in addition to auditory perception: particularly the right PT is involved in stimulus selection and (stimulus-driven), auditory attention.     

Lateralized ultradian rhythms of the right and left brain: temporal variations of tactile discrimination tested in German subjects.

Endogenous ultradian rhythms with a periodicity of 2-3 hours operate separately in the right and left hemispheres of the human brain and modulate physiological functions, perception and cognition. Since sensory pathways from either hand terminate in the contralateral hemisphere, ultradian rhythms of the right and left brain can be monitored by variations in the tactile discrimination of the left and right hand, respectively. Thirteen right-handed German males were tested every 15 minutes for 8 hours. Time series of the tactile error rate determined for the right and left hands oscillate with significantly different ultradian periodicities. Whereas cycles in tactile discrimination of the right hand (left hemisphere) have a periodicity of about 2 hours, tactile discrimination of the left hand (right hemisphere) is modulated by longer periods of about 3 hours. This is interpreted in terms of the overall functional asymmetry of the human brain. Since the left brain is the specialized locus for verbal processing and the right brain for visual-spatial processing, lateralized ultradian rhythms operating in the hemispheres may provide a distinct frame for long-term timing of neuronal processes underlying semantic and spatial mapping of the environment. This is particularly important for interpreting biosocial behavioural rhythms seen in humans living under natural conditions.     

The role of superior temporal cortex in auditory timing

Recently, there has been upsurge of interest in the neural mechanisms of time perception. A central question is whether the representation of time is distributed over brain regions as a function of stimulus modality, task and length of the duration used or whether it is centralized in a single specific and supramodal network. The answers seem to be converging on the former, and many areas not primarily considered as temporal processing areas remain to be investigated in the temporal domain. Here we asked whether the superior temporal gyrus, an auditory modality specific area, is involved in processing of auditory timing. Repetitive transcranial magnetic stimulation was applied over left and right superior temporal gyri while participants performed either a temporal or a frequency discrimination task of single tones. A significant decrease in performance accuracy was observed after stimulation of the right superior temporal gyrus, in addition to an increase in response uncertainty as measured by the Just Noticeable Difference. The results are specific to auditory temporal processing and performance on the frequency task was not affected. Our results further support the idea of distributed temporal processing and speak in favor of the existence of modality specific temporal regions in the human brain.     

Temporal and Motor Representation of Rhythm in Fronto-Parietal Cortical Areas: An fMRI Study

When sounds occur with temporally structured patterns, we can feel a rhythm. To memorize a rhythm, perception of its temporal patterns and organization of them into a hierarchically structured sequence are necessary. On the other hand, rhythm perception can often cause unintentional body movements. Thus, we hypothesized that rhythm information can be manifested in two different ways; temporal and motor representations. The motor representation depends on effectors, such as the finger or foot, whereas the temporal representation is effector-independent. We tested our hypothesis with a working memory paradigm to elucidate neuronal correlates of temporal or motor representation of rhythm and to reveal the neural networks associated with these representations. We measured brain activity by fMRI while participants memorized rhythms and reproduced them by tapping with the right finger, left finger, or foot, or by articulation. The right inferior frontal gyrus and the inferior parietal lobule exhibited significant effector-independent activations during encoding and retrieval of rhythm information, whereas the left inferior parietal lobule and supplementary motor area (SMA) showed effector-dependent activations during retrieval. These results suggest that temporal sequences of rhythm are probably represented in the right fronto-parietal network, whereas motor sequences of rhythm can be represented in the SMA-parietal network.