Opposed attentional hemi-bias on a visuoconstructive task in children with severe hyperactivity versus severe inattention.

Twenty six empirical investigations have now established that children and adults with DSM-defined Attention deficit/Hyperactivity disorder (ADHD) of the Hyperactive type (ADHD-H) or, more commonly, Combined Hyperactive/Inattentive types (ADHD-C) manifest a small but significant visual attentional bias to the right side (left subclinical neglect), consistently suggesting the existence of a subtle right hemisphere dysfunction or hemispheric imbalance in hyperactive people. Only one research team has investigated and compared the DSM-defined Inattentive subtype (ADHD-I) to the Hyperactive subtype (ADHD-H), confirming that line bisection is biased to the right in ADHD-H and discovering that it is biased to the left in ADHD-I. We aimed to test whether a similar crossed double dissociation would extend to Rey's Complex Figure Copy Task (RCF-CT), a simple visuospatial-constructive task. Clinical files of 205 juvenile clients from 6 to 16 years of age from a neuropsychological private clinic specialized in ADHD were analysed. Extreme scores on the Connors-3 Hyperactivity vs Inattention Parent Rating scales associated, respectively, with significant rightward and significant leftward emplacement of the drawing on the page on the RCF-CT. These results replicate previous findings and extend the "energetics" model of hemispheric specialization.

Effects of stimulus pair orientation and hand switching on reaction time estimates of interhemispheric transfer.

Two behavioral estimates of interhemispheric transfer time, the crossed-uncrossed difference (CUD) and the unilateral field advantage (UFA), are thought to, respectively, index transfer of premotor and visual information across the corpus callosum in neurotypical participants. However, no attempt to manipulate visual and motor contingencies in a set of tasks while measuring the CUD and the UFA has yet been reported. In two go/no-go comparison experiments, stimulus pair orientations were manipulated. The hand of response changed after each correct response in the second, but not the first experiment. No correlation was found between the CUD and the UFA, supporting the hypothesis that these two measures index different types of information transfer across hemispheres. An effect of manipulation of stimulus pair orientation on UFAs was attributed to the homotopy of callosal fibers transferring visual information, while an effect of hand switching on CUDs was attributed mostly to spatial compatibility.

Intellectual outcome after a cortical lesion with versus without epilepsy: A life span neurodevelopmental view.

In patients with cortical lesions, the structure of intelligence has never been studied as a function of age at lesion onset and presence vs absence of lesional epilepsy over the life span. METHOD: Two thousand one hundred eighty-six cases were assembled bearing unilateral cortical lesions occurring at all ages (1301 with seizures) with postlesion verbal intelligence quotient (IQ) (VIQ) and performance IQ (PIQ). RESULTS: Global IQ significantly and constantly decreased as a function of age at lesion onset in the cases without epilepsy, and increased in the cases with epilepsy. Beyond the lesion onset age of 12 years, VIQ was significantly higher than PIQ in the cases without epilepsy, and lower in the cases with epilepsy. The VIQ/PIQ × lesion-side interaction indicative of hemispheric specialization increased significantly linearly with age at lesion onset in the patients without epilepsy but ceased to progress at the lesion-onset age of 30 years and beyond in the cases with epilepsy. CONCLUSION: Postlesion global IQ, the difference between VIQ and PIQ, and the laterality index all vary significantly as a function of age at lesion onset. In addition, these changes over the life span are all quite different between cases with and without epilepsy.

Development of "material-specific" hemispheric specialization from beginning to end.

Disparity of verbal and performance intelligence (VIQ, PIQ) on the Wechsler scales of intelligence is a conceptually cluttered and empirically weak measure of hemispheric specialization (HS). However, in the context of life span research, it is the only measure that can be exploited meta-analytically with the lesion method from prenatal life to late senescence. We assembled 1917 cases with a unilateral cortical focal brain lesion occurring at all ages and a post-lesion VIQ and PIQ. Lesion locus, volume and side were documented for each case, as well as age at lesion onset, age at first symptoms and age at the IQ test, presence/absence of epilepsy, lesion aetiology, gender, date of publication or of transfer of medical file. With and without covariate adjustment, HS was significant across the life span though its pattern changed. HS increased linearly and highly significantly until late senescence. Only in early adulthood did VIQ appear to vacate the right temporal lobe and occupy the left and PIQ vacate the left parietal lobe and occupy the right until late senescence. Biomaturational factors are more important in the ontogeny of material-specific HS over the whole life span than previously established.

Callosal Sensitivity to Short-Range Stimulus Orientation and Long-Range Stimulus Context Orientation: Tachistoscopic Evidence.

To study local-global relationships in interhemispheric interactions, tachistoscopically presented pairs of lines (1.15 degrees) were compared for their relative orientation by 48 neurotypical adults. Orientations of line stimuli (local aspect of the task) were vertical, horizontal, forward slash or backslash, as were those of the interstimulus axes. The latter created a global context that could influence line discrimination. Stimulus pairs were presented within a field (not requiring callosal participation for line orientation comparison) or one on each side of the visual field meridian (requiring callosal participation). The primary purpose of the design was to determine whether local or global violations of stimulus "homotopy" across the meridian would impose costs of interhemispheric integration. The rationale for this expectation is that the fiber projection of the corpus callosum is highly symmetric across the midsagittal plane (i.e., homotopic). The expected "callosal homotopy" effect was significantly upheld as a whole but broke down or became extravagant in certain specific conditions, with specific costs of interhemispheric integration varying from null to a highly significant 20-ms as a function of interactions of interstimulus and stimulus orientations. The corpus callosum seems to be particularly sensitive to local stimulus orientation in interaction with long-range stimulus context orientation.

Comparison of two models of hemispheric specialization with unilaterally lesioned patients: material-specific impairment vs response-bias distortion.

Validity of two models of hemispheric specialization was compared. The "material-specific impairment" model was radicalized as postulating that left hemisphere (LH) lesions impair processing of verbal material and that right hemisphere (RH) lesions impair processing of visuospatial material, independently of response-bias distortions. The "response-bias distortion" model was radicalized as postulating that LH lesions distort response style toward omissiveness and that RH lesions distort response style toward commissiveness, regardless of material-specific impairments. Participants had comparable left (N=27) or right (N=24) hemisphere cortical lesions having occurred between birth and early adolescence. Four cognitive neuropsychological tests were adjusted to optimize applicability and comparability of the two theoretical models: Rey Complex Figure, Kimura's Recurring Figures, the Story Recall subtest of the Children's Memory Scale, and the California Verbal Learning Test. Both models significantly, independently, and equally distinguished the LH from the RH patients. Both these forms of hemispheric specialization seemed to be implemented very early in life and very rigidly. Intrahemispheric lesion sites, e.g., frontal vs nonfrontal, held no significant relation to the effects described above.

Atypical left-right balance of visuomotor awareness in adult ADHD (combined type) on a test of executive function.

Significant left subclinical hemi-neglect or "hemi-unawareness" in juvenile and adult ADHD has been reported many times. However, this literature has never been thoroughly reviewed, and is generally ignored in neuropsychological accounts of ADHD. The purposes of the present report were (1) to introduce a systematic review of this literature and (2) to prospectively test whether adults with ADHD (combined type) would present left hemi-unawareness measurable on a test of executive function commonly used with children and adults with ADHD, the Colour-Word Interference Test of the Delis-Kaplan Executive Functions System. This test requires participants to discriminate unusual stimulus characteristics by stating words aloud while visually scanning plates comprising either 50 colour patches or 50 words. A total of 28 ADHD adults (combined type) and 30 IQ-, age-, and gender-matched controls completed the task. The ADHD group manifested a significantly higher proportion of errors on the left than right sides of the plates. This atypical left-right balance was related to severity of the ADHD according to the Conners' Adult ADHD Rating Scale (CAARS) as well as to several other indicators from the Continuous Performance Test-II.

Opposed hemispheric specializations for human hypersexuality and orgasm?

With a multiple case report analysis we demonstrate that hypersexuality more often results from right hemisphere (RH) (n=26) than left hemisphere (LH) (n=7) lesions, possibly because of LH release after the RH lesion, and that ictal orgasm more often occurs in patients with right-sided (n=23) than left-sided (n=8) seizure foci, with the symptom probably resulting from RH activation. The LH may be specialized for increasing sexual tension, whereas the RH may be specialized for release of this tension (orgasm), the former being catabolic and the latter anabolic. Several other interpretations of the findings are also discussed.

A general neuropsychological model of delusion.

INTRODUCTION: Neurocognitive accounts of delusion have traditionally highlighted perceptual misrepresentation, as the primary trigger in addition to other cognitive deficits that maintain the delusion. Here, a general neurocognitive model of delusional disorder (DSM-IV) is proposed, not so much based on perceptual or cognitive deficits after right hemisphere damage as on cognitive propensities, specifically excessive inferencing (especially jumping to conclusions) and excessive reference to the self, due to left hemisphere overactivity. METHOD: The functional imaging, topographic EEG, and experimental imaging literatures on delusional disorder are reviewed, and 37 previously published cases of postunilateral lesion delusion (DSM-IV type, grandeur, persecution, jealousy, erotomania, or somatic), are reviewed and analysed multivariately. RESULTS: Functional imaging and EEG topography data were slightly more indicative of left hemisphere overactivity in delusional disorder. In addition, 73% of the postunilateral lesion cases (χ(2)=7.8, p=.005) of delusional disorder (DSM-IV type) had a right hemisphere lesion, whereas only 27% had a left hemisphere lesion. CONCLUSION: Left hemisphere release appears to be a more primary cause of delusional disorder than right hemisphere impairment, the latter merely entailing loss of inhibition of delusional beliefs. We propose that most patients with DSM-IV diagnoses of delusional disorder could be afflicted by excessive left hemisphere activity, but further research is necessary.

New variations of intrahemispheric and interhemispheric processing indexed by the dimond paradigm.

We report 2 experiments designed to demonstrate that unilateral tachistoscopic stimulation would yield a response time (RT) advantage over bilateral stimulation in a simple experiment, whereas the opposite pattern would occur in a complex version of the same task, as predicted by the intrahemispheric resource limitation model of Banich and colleagues. Experiment 1 was a go/no-go task in which participants had to press a key when two shapes (circles or squares) were identical on the computer screen. A unilateral field advantage was obtained that was accentuated in several task conditions that yielded overall longer RTs, mostly in the bilateral condition. Experiment 2 was similar but required a more complex judgment: The go trials were to 2 stimuli identical on 1 dimension (shape or color) but not both or neither. The RTs were significantly and substantially longer than in Experiment 1 and exhibited a nonsignificant bilateral field advantage, which differed significantly from the unilateral field advantage obtained in Experiment 1. These results support the intrahemispheric resource limitation model of Banich and colleagues. However, several within-experiment effects are in direct opposition to this model and are best explained as limitations of commissural relay of perceptual information.

A choice reaction time index of callosal anatomical homotopy.

Tachistoscopically presented bilateral stimulus pairs not parallel to the meridian produced significantly longer RTs on a task requiring discrimination of shapes (Go/no-Go) than pairs emplaced symmetrically on each side of the meridian in Desjardins and Braun [Desjardins, S., & Braun, C. M. J. (2006). Homotopy and heterotopy and the bilateral field advantage in the Dimond paradigm. Acta Psychologica, 121, 125-136]. This was explained by the fact that there are more homotopic than heterotopic fibers in the corpus callosum. However: (1) different parts of the visual field were not equiprobably stimulated, possibly causing subtle biases, (2) the predicted cost of vertical asymmetry was tested only with bilateral stimuli, and (3) interstimulus distance was at the outer limit of callosal midline fusion (10.6 degrees ). Here, a tachistoscopic experiment with 24 normal participants replicated the between-field vertical symmetry advantage [Desjardins, S., & Braun, C. M. J. (2006). Homotopy and heterotopy and the bilateral field advantage in the Dimond paradigm. Acta Psychologica, 121,125-136.], but without irrelevant stimulation conditions and with more proximal stimuli. In addition, a significant specific cost of vertical asymmetry of 7ms was found for between-field integration over within-field integration. As far as we know, this is the first demonstration of an effect of callosal anatomical homotopy with reaction time.

Post unilateral lesion response biases modulate memory: crossed double dissociation of hemispheric specialisations.

We propose that what appears to be hemispheric specialisation in the memory domain, as indexed by effects of unilateral brain lesions, is to a great extent explainable as response bias: left hemisphere lesions result in an omissive response bias or error pattern whereas right hemisphere lesions result in a commissive response bias or error pattern. To test this prediction a group of 40 non-confabulatory cases with a verbal and non-verbal retention deficit (hypomnesia), subsequent to a unilateral lesion, was assembled from the literature. A group of non-amnesic cases with confabulation, paramnesia, false memories or memory-laden hallucination (dysfunctional hypermnesia), due to a unilateral lesion, was also assembled from the literature (N=72). Most of the hypomnesic patients had left hemisphere lesions (73%, p<.005, two tailed) while most of the hypermnesic patients had right hemisphere lesions (78%, p<.0005, two tailed). This crossed double dissociation held good despite statistical control of the lesion's locus within the hemisphere, its size or its aetiology, presence of aphasic symptoms, psychiatric comorbidity, the patient's age, gender, or hand preference, and several other potentially confounding variables.

Dream content analysis in persons with an autism spectrum disorder.

Dream questionnaires were completed by 28 young adults with autism spectrum disorder (ASD) participants. Seventy-nine typically developed individual served as the control group. In a subset of 17 persons with ASD and 11 controls matched for verbal IQ, dream narratives were obtained following REM sleep awakenings in a sleep laboratory. Questionnaires revealed that participants with ASD, compared to controls, had fewer recollections of dreaming, fewer bad dreams and fewer emotions. In the sleep laboratory, dream content narratives following REM sleep awakenings were shorter in ASD participants than in controls. ASD participants also reported fewer settings, objects, characters, social interactions, activities, and emotions. It is concluded that these characteristics of dreaming in ASD may reflect neurocognitive dimensions specific to this condition.

Brain lesions and IQ: recovery versus decline depends on age of onset.

A growing literature suggests that early lesions are associated with poorer IQ outcome. Those studies covered a restricted age range in pediatric populations only and did not control for important moderator variables. The present investigation studied IQ change in brain-lesioned children and adults (age 0 to 84 years). Altogether, 725 cases with a documented unilateral focal lesion were gathered from hospital charts and from published cases in the literature, including 240 with repeated IQ testing. Multiple regression analyses isolated the contribution of age at lesion onset to IQ change. Important mediator variables included were lesion side, site, volume, etiology, and so on. An early lesion was significantly associated with poorer postlesion IQ in time and with decline of IQ in time. Later onset lesions were associated with better postlesion IQ and recovery in time. The so-called Kennard principle is refuted, with regard to IQ.

Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition symptoms of mania: which one(s) result(s) more often from right than left hemisphere lesions?

Previously published single case reports of patients with a unilateral lesion were assembled. After the lesion, each of the 244 cases presented at least one of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) symptoms of a manic episode, namely, elated or irritable mood, grandiosity, talkativeness, flight of ideas, hyperhedonism, reduced need for sleep, agitation, or distractibility (all optional in DSM-IV). As expected, the subgroup of 59 manic patients had a right hemisphere lesion far more often than a left one. However, this was also true of various sets of the nonmanic cases. Furthermore, elation was not the symptom most strongly associated with lesion side. Elation without mania was not significantly predicted by lesion side. However, talkativeness was strongly predicted by right lesion side whether in manic or nonmanic patients or even when the symptom was the only symptom observed. Agitation was consistently and robustly associated with right lesion side, but not completely distinctly so (it fell short of significance when not accompanied by elation or other symptoms). It is proposed that prevalence of right hemisphere lesions causing mania is primarily related to mental and behavioral disinhibition rather than a shift of mood and that it consists of release of left hemisphere influence.

Ictal fear depends on the cerebral laterality of the epileptic activity.

Glascher and Adolph (2003) proposed that both amydalae are specialized for fear, but that the right one is a fast, short, and relatively automatic fear processor, whereas the left one is more detail-oriented and perceptual-cognitive. According to this model, early ictal fear should occur more often in cases with a right temporal lobe epileptic focus. Several authors have tried to find a hemispheric specialization for ictal fear, but have not reached the power to attain a statistically significant effect of focus side. In this study, using previously published cases of unilateral epileptic focus causing early ictal symptoms of fear, we found 144 cases, of which 98 had a right hemisphere focus (68%) and 46 having left hemisphere focus (32%, p < 0.0005). Several control variables were assembled to verify possible alternative explanations of the main effect.

Visual hypo and hypergnosia as exemplars of poles of psychic tonus in the occipital lobes: multiple case analyses.

The "psychic tonus" model or PTM [1] of hemispheric specialization states that the left hemisphere is a psychic and behavioral activator and that the right hemisphere is an inhibitor. The PTM predicts that the tonus of visual representation ought to manifest hemispheric specialization in the occipital lobes. Specifically PTM predicts that pathological positive visual tonus (visual hallucination) ought to be associated more frequently with right occipital lesions. PTM also predicts that pathological negative visual tonus (loss of visual imagery) ought to result more often from left occipital lesions. We reviewed 78 cases of post lesion hallucination and 12 cases of post lesion loss of evocation of images, all following a unilateral lesion. Analyses of these relevant previously published cases support the predictions. In accordance with previously published demonstrations of hemispheric specialization for auditory tonus in the temporal lobes and for somesthetic tonus in the parietal lobes, the present findings extend the psychic tonus model of hemispheric specialization to vision in the occipital lobes.

An orbitofrontostriatopallidal pathway for morality: evidence from postlesion antisocial and obsessive-compulsive disorder.

INTRODUCTION: A detailed proposal is made to the effect that nonlesional antisocial personality disorder (APD) is, among other things, a dysfunctional hypomoralism and that nonlesional obsessive-compulsive disorder (OCD) is, among other things, a dysfunctional hypermoralism. METHOD: To provide an empirical test of this proposal, 25 previously published cases of acquired (post lesion) APD and 39 cases of acquired OCD are reviewed and compared with multivariate inference tests. RESULTS: The acquired APD patients most often present putamenal or pallidal lesions. CONCLUSION: The ensemble of neurobiological, endocrine, and behavioural traits in APD and OCD, as well as the distinct lesion sites in the acquired variants, support the notion of an orbitofrontostriatopallidal brain system underlying morality.

The relative importance of suboperations of prospective memory.

An event-based and a time-based prospective memory (PM) task, a script generation task, several working memory tasks, an incidental retrospective memory task, and a screen clock were implemented on the computer in one integrated procedure lasting between one and two hours. The procedure was designed to simulate four working days and four nights for a white-collar employee. Sixty-eight normal participants completed the task. Time-based prospective memory (self-injecting and going to bed at preordained times of day) shared unique variance with clock checking, but hardly at all with incidental retrospective memory. On the other hand, event-based prospective memory (answering a faint telephone cue as quickly as possible) shared unique variance with incidental retrospective memory of formally task irrelevant context and less with clock checking. The latter correlational dissociation of event-based versus time-based PM by retrospective memory reached significance, inspiring the idea that administrative versus clerical work might each impose its own type of PM demands. In both types of PM, low-level abilities (use of external aids and incidental encoding of context, respectively) seem to be critical for good performance, more so than for high-order executive functions. Our software is offered to the readership to explicitate these findings further or for other research pursuits.

Reaction Time of Erroneous Responses in the Go/No-Go Paradigm.

Reaction time (RT) of erroneous responses in go/no-go tasks tends to be shorter than RT of correct responses. An opposite difference has been reported ( Halperin, Wolf, Greenblatt, & Young, 1991 ) which could be attributed to differences in go trial probability, or to high memory demand. Two experiments aimed here to test these two explanations, a simultaneous matching task with low memory load (Experiment 1), and a sequential matching task with high memory load (Experiment 2). Go trial probability was also manipulated. Short false positive RT was obtained only in the sequential matching task with high go trial probability, while long false positive RT was obtained in the other three conditions. Low go trial probability and high memory load were both found to be sufficient, by themselves, to create long false positives attributable to confusion. Short false positives in the high go trial probability/low memory load condition were attributed to failure of response inhibition.