Dichotic listening with forced attention in patients with temporal lobe epilepsy: significance of left hemisphere cognitive dysfunction

Fifty right-handed patients with focal temporal lobe epilepsy were administered a dichotic listening test with consonant-vowel syllables under non-forced, forced right and forced left attention conditions, and a neuropsychological test battery. Dichotic listening performance was compared in subgroups with and without left hemisphere cognitive dysfunction, measured by the test battery, and in subgroups with left and right temporal epileptic focus. Left hemisphere cognitive dysfunction led to more correct responses to left ear stimuli in all three attention conditions, and fewer correct responses to right ear stimuli in the non-forced attention condition. This was probably caused by basic left hemisphere perceptual dysfunction. Dichotic listening was less affected by a left-sided epileptic focus than by left hemisphere cognitive dysfunction. General cognitive functioning influenced dichotic listening performance stronger in forced than in non-forced attention conditions. Larger cerebral networks were probably involved in the forced attention conditions due to the emphasis on conscious effort.     

Sources of performance on theory of mind tasks in right hemisphere-damaged patients

Patients with right hemisphere (RHD) or left hemisphere brain damage (LHD) were tested on Theory of Mind (ToM) tasks presented with visual aids that illustrated the relevant premises. As a measure of pragmatic ability, patients were also asked to judge replies in conversation that violated Gricean maxims. Both RHD and LHD patients performed well on the ToM tasks presented with visual aids, but RHD patients displayed difficulty when the same tasks were presented only verbally. In addition, RHD patients showed reduced sensitivity to pragmatic violations. These findings point to the role of right hemisphere structures in processing information relevant to conversations. They indicate that a crucial source of RHD patients' errors in ToM tasks may involve difficulties in utterance interpretation owing to impairments of visuospatial processing required for the representation of textual information.     

Dissociations among memory measures in memory-impaired subjects: Evidence for a processing account of memory

Deficits in conceptual transfer on both implicit and explicit memory tests were obtained for memory-impaired temporal lobe epileptic (TLE) subjects in three studies. In Experiment 1, in which a generate-read paradigm was employed, memory-impaired TLEs failed to show normal generation effects on conceptually driven tests of semantic cued recall and general knowledge questions, although their data-driven memory as measured by word-fragment completion and graphemic cued recall tasks was normal. In Experiment 2, memory-impaired patients having left temporal lobe seizure foci were tested on these four tasks and compared with nonimpaired TLEs having right temporal foci. The left TLEs showed deficits on conceptually driven tasks and normal memory for data-driven tests. These findings were extended in Experiment 3, in which left TLE patients failed to show any benefit from blocked study, as compared with random study, on category production and semantic cued-recall tests, although right TLEs and normal controls showed blocking effects on both tasks. These findings may be accommodated by a processing framework of memory in which memory-impaired patients are characterized as having deficits in conceptual, but not in data-driven, processing capabilities.     

Neurodevelopmental differences in emotional prosody in normal children and children with left and right temporal lobe epilepsy

Emotional prosody, which has been defined as the emotional aspects of speech which communicate pleasure, fear, sorrow, anger, etc., has been demonstrated to be primarily a function of the nondominant hemisphere (typically, the right hemisphere) in adult populations. However, few researchers have addressed the developmental or lateralized nature of emotional prosody in children. In this study, an instrument was developed to measure the receptive aspects of emotional prosody in pediatric populations and administered to normal children ages 6 to 11 years old. An analysis of variance revealed significant age-related differences. Additionally, the instrument was administered to 12 children with right temporal lobe epilepsy and 11 children with left temporal lobe epilepsy. Analysis of variance indicated that there was no significant difference in scores between the left temporal and right temporal lobe groups. However, right temporal epileptic patients scored significantly lower than normal children on all sections of the instrument, suggesting that in children like adults, the right temporal lobe may be dominant with respect to the receptive aspects of emotional prosody.     

Radial bisection of words and lines in right‐brain‐damaged patients with spatial neglect

The bisection of lines positioned radially (with the two ends of the line close and far, with respect to the participant's body) has been less investigated than that of lines placed horizontally (with their two ends left and right, with respect to the body's midsagittal plane). In horizontal bisection, patients with left neglect typically show a rightward bias for both lines and words, greater with longer stimuli. As for radial bisection, available data indicate that neurologically unimpaired participants make a distal error, while results from right‐brain‐damaged patients with left spatial neglect are contradictory. We investigated the bisection of radially oriented words, with the prediction that, during bisection, linguistic material would be recoded to its canonical left‐to‐right format in reading, with the performance of neglect patients being similar to that for horizontal words. Thirteen right‐brain‐damaged patients (seven with left spatial neglect) and fourteen healthy controls were asked to manually bisect 40 radial and 40 horizontal words (5–10 letters), and 80 lines, 40 radial and 40 horizontal, of comparable length. Right‐brain‐damaged patients with spatial neglect exhibited a proximal bias in the bisection of short radial words, with the proximal part corresponding to the final right part of horizontally oriented words. This proximal error was not found in patients without neglect and healthy controls. For bisection, short radial words may be recoded to the canonical orthographic horizontal format, unveiling the impact of left neglect on radially oriented stimuli.     

Short-term and long-term memory deficit following intracarotid Amytal injection: Further support for the memory consolidation hypothesis

To test the three main hypotheses of the human amnesic syndrome (encoding, consolidation, retrieval), we designed an original protocol for memory assessment under Amytal that included, in addition to a retrograde memory measure, both short-term and long-term anterograde memory measures. Twenty epileptic patients with SEEG-confirmed unilateral temporal lobe foci were given right and left injections on successive days. Only the long-term memory measure for material presented under Amytal was significantly related to the presence of a temporal contralateral epileptogenic focus, even if it was assessed when the hemisphere had completely recovered from the effect of Amytal. Short-term memory deficits were observed equally often after injections ipsilateral and contralateral to the epileptogenic focus, and no retrograde amnesia was observed. These results are consistent with the consolidation hypothesis.     

Memory deficits during electrical stimulation of the speech cortex in conscious man

Cerebral zones supporting language and recent memory were mapped by electrical stimulation during neurosurgical treatment of epileptic patients. Stimulation of sites within the left posterior temporo-parietal cortex produced transient dysphasia. Continued stimulation of this cortical region also produced a retrograde type of verbal memory disorder, indicating a failure in the mechanism responsible for retrieval of stored information. In contrast, stimulation of the anterior temporal neocortex did not produce anomia and, instead, resulted in an anterograde memory loss, apparently caused by a defect in the verbal storage mechanism. Comparable stimulation of homologous areas on the right hemisphere did not interfere with object naming or immediate verbal recall.     

Building higher-order units in tachistoscopic identification: A test of two models

Summary Subjects were shown eight-letter pseudowords tachistoscopically and were asked to report as many letters as possible. The pseudowords, examples of either first- or fourth-order approximation to English, were printed in normal or reversed spelling and were presented in either normal of mirror-imaged letters. Finally subjects were either free to report in any order they wished, or they were instructed to report from left to right or from right to left. With normal letters, the familiarity effect was controlled by the spelling direction, not by the direction of report or the match between direction of report and spelling direction. With mirrored letters, however, order of approximation to English had no effect. The results contradict two existing theories: Mewhort's theory claims that the familiarity of fourth-order materials aids processing at a postcategorical level; it has trouble explaining why the familiarity effect disappeared with mirrored letters and normal spelling. Wolff's theory claims that familiarity aids processing at the feature level; it has trouble explaining why the familiarity effect disappeared with mirrored letters and reversed spelling.     

Right and left hemisphere cooperation for drawing predictive and coherence inferences during normal story comprehension

In three experiments, healthy young participants listened to stories promoting inferences and named inference-related test words presented to the right visual field-Left Hemisphere (rvf-LH) or to the left visual field-Right Hemisphere (lvf-RH). Participants showed priming for predictive inferences only for target words presented to the lvf-RH; in contrast, they showed priming for coherence inferences only for target words presented to the rvf-LH. These results, plus the fact that patients with RH brain damage have difficulty drawing coherence inferences and do not show inference-related priming, suggest that information capable of supporting predictive inferences is more likely to be initially activated in the RH than the LH, but following coherence breaks these concepts (now coherence inferences) are completed in the LH. These results are consistent with the theory that the RH engages in relatively coarse semantic coding, which aids full comprehension of discourse.     

Right hemisphericity, low self-esteem, and unusual experiences: a response to Vingiano.

Vingiano's (1992) challenge concerning the relationship between right hemisphericity, low self-esteem, mystical experiences, and religiosity can be clarified by the concept of vectorial hemisphericity. Ontogenetic intrusions of right-hemispheric processes into the left hemispheric sense of self should be experienced most frequently as an apprehensive "presence" that results in lower self-esteem. Because transient above-normal left-hemispheric activity enhances positive affect and the sense of self, concurrent right-hemispheric intrusions are experienced as mystical experiences. Religiosity would be the consequence of persistent above-normal left-temporofrontal activation that encourages the delusion. Hence, extreme conditions, such as left lateralized temporal-lobe epileptic foci, encourage both mystical and religious experiences.     

Inter-limb coupling in bimanual rhythmic coordination in Parkinson's disease

Recently, it has been shown that rhythmic inter-limb coordination is disturbed in patients with Parkinson's disease (PD). The present study aims to investigate whether this coordination deficit is primarily the result of an impaired coupling, related to hypoactivation of the supplementary motor area (SMA), or primarily the indirect result of an asymmetrical distribution of PD symptoms over the left and right limbs (a peripheral process). Thirty PD patients and 30 matched control participants tapped with the index fingers anti-phase and left and right leading gallop patterns in four visual feedback conditions. Symmetrically affected participants performed significantly worse than asymmetrically affected and control participants in the gallop patterns. This result suggested that the central deficit has a stronger effect on inter-limb coupling in PD than the neuromuscular and biomechanical asymmetry between the limbs. Detailed analysis of inter-tap intervals (variability and correlation) suggested that this deficit leads to a compensatory asymmetrical inter-limb coupling in the primarily right-affected patient group, and under specific circumstances also in the primarily left-affected patient group. The difference in coordination strategy between left- and right-affected patients suggested that pre-morbid hand preference is an important structural constraint on the coupling strategies available to the participants.     

Functional connectivity abnormalities vary by amygdala subdivision and are associated with psychiatric symptoms in unilateral temporal epilepsy

The amygdala has been described as a structure affected by mesial temporal lobe epilepsy (MTLE). Indeed, it is suggested that amygdala abnormalities are related to the co-morbid depression and anxiety reported in MTLE. In this context, we investigated the relation between functional connectivity (FC) emerging from this structure in fMRI and depression and anxiety levels reported in MTLE patients. We focused on resting-state BOLD activity and evaluated whether FC differences emerge from each of three amygdala subdivisions (laterobasal, centromedial and superficial) in left and right MTLE groups, compared with healthy controls. Results revealed significant differences between patient groups and controls. Specifically, the left MTLE group showed abnormal FC for the left-sided seeds only. Furthermore, regardless of the seed, we observed more reliable differences between the right MTLE group and controls. Further analysis of these results revealed correlations between these impaired connectivities and psychiatric symptoms in both MTLE groups. Opposite relations, however, were highlighted: the more depressed or anxious the right MTLE patients, the closer their FC values approached controls; whereas the less anxious the left MTLE patients, the closer their FC values were normative. These results highlight how MTLE alter FC emerging from the limbic system. Overall, our data demonstrate that right TLE has a more maladaptive impact on emotion-related networks, in ways specific to the amygdala region, and the emotion symptom involved, than left TLE.     

Plasticity of the callosal system

A series of experiments examined the potential plasticity of the callosal system in both epileptic patients and in kittens submitted to corpus callosotomy at various ages. The patients were tested for unilateral discrimination and interhemispheric transfer of tactile information. The youngest patient was also required to perform additional inter- and intrahemispheric comparisons of visual and tactile stimuli. The animals were tested for interhemispheric transfer of visual discriminations. The results suggest that in both animals and humans there exists a critical period before which callosal section does not disrupt interhemispheric communication. The results also indicate that the compensatory mechanisms used to achieve interhemispheric transfer in the absence of the corpus callosum may vary according to the sensory modality involved. The possible physiological and/or functional mechanisms responsible for callosal plasticity are discussed.     

Modeling change in memory performance and memory perceptions: findings from the ACTIVE study

Within the context of the ACTIVE study, the current investigation explored the relationships between objective memory and two components of subjective memory (frequency of forgetting and use of external aids) over a five-year period. Relationships were assessed using parallel process latent growth curve models. Results indicated that changes in objective memory were associated with changes in perceived frequency of forgetting, but not with use of external aids (calendars, reminder notes) over time. Findings suggest that memory complaints may accurately reflect decline in objective memory performance, but that these memory changes are not necessarily related to compensatory behaviors.     

Opposed left and right brain hemisphere contributions to sexual drive: a multiple lesion case analysis

Brain topographical studies of normal men have have shown that sexual excitation is asymmetric in the brain hemispheres. Group studies of patients with unilateral epileptic foci and other studies of patients with unilateral brain lesions have come to the same conclusion. The present study reviewed previously published single case reports of patients with frank hypo or hypersexuality subsequent to a unilateral brain lesion. Hyposexual patients tended to have left hemisphere lesions (primarily of the temporal lobe), and hypersexual patients tended to have right hemisphere lesions (primarily of the temporal lobe) (p < 0.05). We interpret this double dissociation as part of a more general phenomenon of psychic tone similarly dissociated with regard to hemispheric control, including mood, psychomotor baseline, speech rate, and even immunity. The behavioral significance of this psychic tone is to modulate approach versus avoidance behavior.     

"白痴学者"之谜的哲学思考

提出解释白痴学者之谜的"左右脑发育不平衡假说".假说认为,白痴学者的独特思维特征源于左右脑的不平衡发育--白痴学者的左脑发育不全,偿补性地促使右脑得到充足发育,在一定环境条件下,诱发产生了白痴学者这一异常思维现象.根据假说,文章对白痴学者所表现的种种事实特征逐一加以解析说明.     

Ambiguous emotion recognition in temporal lobe epilepsy: The role of expression intensity

The lateralization of emotion processing is currently debated and may be further explored by examining facial expression recognition (FER) impairments in temporal lobe epilepsy (TLE). Furthermore, there is also debate in the literature whether FER deficits in individuals with TLE are more pronounced in the right than in the left hemisphere. Individuals with TLE were tested with an FER task designed to be more sensitive than those classically used to shed light on this issue. A total of 25 right- and 32 left-TLE patients, candidates for surgery, along with controls, underwent an FER task composed of stimuli shown not only at full-blown intensities (100 %), but also morphed to lower-intensity display levels (35 %, 50 %, and 75 %). The results showed that, as compared to controls, right-TLE patients showed deficits in the recognition of all emotional categories. Furthermore, when considering valence, right-TLE patients were impaired only in negative emotion recognition, but no deficits for positive emotions were highlighted in left-TLE patients. Finally, only the right-TLE patients’ impairment was found to be related to the age of epilepsy onset. Our work demonstrates that the FER deficits in TLE span multiple emotional categories and show manifestations dependent on the laterality of the epileptic focus. Taken together, our findings provide the strongest evidence for the right-hemisphere model, but they also partially support the valence model. We suggest that current models are not exhaustive at explaining emotional-processing cerebral control, and further that multistep models should be developed.     

Interictal and postictal performances on dichotic listening test in children with focal epilepsy

Dichotic listening test (DL) is an important tool to disclose speech dominance in healthy subjects and in clinical cases. The aim of this study was to probe if focal epilepsy in children reveals a corresponding suppression of the ear reports contralateral to seizure onset site. Thus, 15 children and adolescents with clinically and electroencephalographically diagnosed focal epilepsy selected for left-hemisphere speech dominance without mental retardation were compared to matched controls according to age, gender, IQ and handedness. All children were assessed with DL for three times: Interictally (t(0)), postictally 5' (t(1)) and 1h (t(2)). At t(0), all groups revealed a right ear advantage (REA), indicating a left-hemisphere speech dominance. There was a continuous increase in right correct score (REC) over the trials for normal controls. Five minutes postictally, there was an abrupt decrease in REC with a sustained left ear correct score (LEC) for children with epilepsy, independent of which side suffered from seizures. This effect was maintained even after 1h. Thus, in children with left-hemisphere speech dominance the epileptic discharges caused a suppression of REC regardless of origin. The seizures may have a prolonged impact on attention and auditory perception for a considerable time after consciousness has been regained.     

Enhanced left frontal involvement during novel metaphor comprehension in schizophrenia: Evidence from functional neuroimaging

The neural basis involved in novel metaphor comprehension in schizophrenia is relatively unknown. Fourteen people with schizophrenia and fourteen controls were scanned while they silently read novel metaphors, conventional metaphors, literal expressions, and meaningless word-pairs. People with schizophrenia showed reduced comprehension of both novel and conventional metaphors. Furthermore, while controls showed enhanced brain activation in right inferior frontal gyrus (IFG) for novel metaphors versus meaningless word-pairs, people with schizophrenia showed an over-activation of left IFG and middle frontal gyrus (MFG). Direct comparison between the groups revealed greater activation in left precuneus for both novel metaphors and literal expressions vs. baseline for individuals with schizophrenia. Direct comparison for novel metaphors vs. literal expressions also revealed increased activation for individuals with schizophrenia in left MFG. These results suggest that the inefficient processing of novel metaphors in schizophrenia involves compensatory recruitment of additional brain regions that include the left MFG and left precuneus.