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.

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).

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

Unlabelled: 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.

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.

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.

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.

Inter-hemispheric dynamics revealed by reaction time in the Dimond paradigm.

The Dimond paradigm (DP) consists of tachistoscopically presenting two stimuli to be discriminated--either both stimuli in a single visual hemifield or one in each. The DP has recently been implemented using predecessors to index homotopy of the callosal fibre projection with reaction time (RT) as the dependent measure. Using simple perceptual discrimination tasks, it has recently been reported that the advantage of the unilateral stimulation condition significantly decreases with practice.

Gender-related protection from or vulnerability to severe CNS diseases: gonado-structural and/or gonado-activational? A meta-analysis of relevant epidemiological studies.

Background: A vast scientific literature has dealt with gender-specific risk for brain disorder. That field is evolving toward a consensus to the effect that the estrogen hormone family is outstandingly and uniquely neuroprotective. However, the epidemiology relevant to this general outlook remains piecemeal.

Intra and inter hemispheric dynamics revealed by reaction time in the Dimond paradigm: a quantitative review of the literature.

In stimulus matching tasks requiring discrimination of two unilaterally or bilaterally presented stimuli (Dimond paradigm), a well established intrahemispheric processing bottleneck model predicts that an increase in task difficulty as measured by reaction time should provide an advantage to bilateral stimulations. The purpose of the current investigation was to review the entire relevant literature on the Dimond paradigm and identify the experimental variables which reliably yield such effects. Forty nine experimental effects compatible with the "intrahemispheric processing bottleneck" model and 26 contrary effects were found.

Evidence from unilateral lesions of early uncompensable implementation of opposed response-biases in each hemisphere of the brain.

Purpose: The intact right hemisphere presents an omissive response-bias and the left hemisphere a commissive response-bias in adults. This research sought to determine whether these hemispherically lateralized response-biases manifest early developmental and uncompensable brain implementation.

Methods: Sixteen teenager and adult participants with focal left hemisphere lesions and fourteen with focal right hemisphere lesions (all with childhood onset: M=13 year recovery period) and 14 normal control participants were recruited.

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.

EEG amplitude spectra before near threshold visual presentations differentially predict detection/omission and short-long reaction time outcomes.

Performance in simple stimulus detection manifests as both probability of detection and speed of signaling detected stimuli. These two dimensions of performance across trials were examined with respect to brain states just prior to stimulus delivery, using near threshold stimuli targeting the magnocellular or the parvocellular visual streams in an attempt to isolate differential perceptual preparation. The EEG amplitude of 12 university students was analyzed in spectral bands from 2 to 50 Hz at 9 bilateral channel pairs in a window covering -450 ms to +50 ms relative to stimulus onset.

Specific early vulnerability of high-order executive function to focal brain lesions and long-term impact on educational persistence: Sparing of incidental episodic memory.

Objective: We investigated mental functions expected to remain impaired or not ain adulthood following childhood-onset brain lesions.

Methods: Thirty unilaterally lesioned young adults were tested a decade after lesion onset with an effort-demanding complex executive function (EF) task as well as a task of incidental declarative retrospective episodic recognition memory (IRM). Thirty neurotypical participants were also tested.

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.

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.

A context for normalizing impulsiveness at work for adults with attention deficit/hyperactivity disorder (combined type).

Impaired executive function and impulsiveness or intolerance to boredom in adult attention deficit/hyperactivity disorder (ADHD) are thought to compromise performance at work. Several task parameters help people with ADHD to perform better on computerized cognitive tasks, namely reduced response-to-stimulus interval, discriminative feedback, or a format resembling a videogame. However, still very little is known about how these contexts might be helpful in a real work environment.

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.

A verbal planning impairment in adult ADHD indexed by script generation tasks.

Objective: Though juvenile and adult ADHD cases are well known to have a nonverbal planning impairment, a verbal-planning impairment has been demonstrated only in juvenile ADHD. The purpose of this investigation is to determine whether a verbal planning impairment also characterizes adult ADHD.

Methods: A cohort of 30 adult ADHD clients of a university psychological clinic are compared to 30 age-, education-, gender-, and IQ-matched persons recruited from the general population who did not have ADHD.

Ictal hallucination and hemispheric specialization: findings from 217 cases with a unilateral epileptic focus.

Epileptic populations are generally considered inappropriate to investigate hemispheric specialization. However, (1) because hallucination occurs in the early stage of the ictus during which activation is observed in and around the focus, the former could be a direct result of the latter (hypothesis 1), and (2) the type of psychological content of ictal hallucination could depend on which hemisphere is ictally activated (hypothesis 2). It was predicted that, on the basis of quantitative analysis of previously published singles case reports, unilateral ictal hallucinations should occur in the visual field, ear or hemibody contralateral to the side of the ictal focus (test of hypothesis 1).

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.

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.

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).

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.

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.