Anik Guimond

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.

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.

Remembering the Past and Foreseeing the Future while Dealing with the Present: A Comparison of Young Adult and Elderly Cohorts on a Multitask Simulation of Occupational Activities

Thirty-five young adult and 38 elderly cybernauts, matched for education, sex, alcohol consumption, and time/day of computer use were compared on a computerized simulation of professional activities of daily living (ADLs). The program quantified performance in terms of speed and accuracy on four major constructs: (1) planning (a 30-item office party script); (2) prospective memory (injections, sleep, phone); (3) working memory (PASAT, D2, and CES analogs); and (4) retrospective memory. Participants had to organize an office party, self inject insulin and go to bed at requisite times of day, do “office work” at unpredictable times of day, and answer the phone that blinked but did not ring (near threshold stimulus). The elderly were markedly and equally impaired on all four constructs (F = 24.3, p < .000). The elderly were also equally and markedly impaired on slave and central executive systems (c.f. Baddeleys model) and on event-based and time-based prospective memory (c.f. McDaniels model)—findings arguing against a “frontal” model of cognitive decline. This supports Salthouses concept of a “general factors” decline in normal aging due to diffuse deterioration of the brain. On the other hand, as expected from previous findings, the balance of omissiveness/commissiveness was significantly increased in the elderly samples error profile. Furthermore, the balance of speed and accuracy was significantly increased in the elderly. This defines limits of the “general factors” model. The elderly also markedly underused a clock icon which had to be clicked on to get the virtual time of day necessary for integrating all the required actions. Prospective memory explained 11% of the aging variance despite partialing out of the three other constructs, making it appear as a golden standard of sensititivity to normal aging—though perhaps provided it be implemented in a distracting, multitask, strategically demanding context.

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.

Psychic Tonus, Body Schema and the Parietal Lobes: A Multiple Lesion Case Analysis

The psychic tonus model (Braun and colleagues, 1999, 2002, 2003, 2006) states that the left hemisphere is a “booster” of internal experience and behavior in general, and that the right hemisphere is a “dampener”. Twenty-five patients with a “positive” extreme disturbance of body schema (somatoparaphrenia) and 37 patients with a “negative” disturbance of body schema (autotopagnosia or Gerstmann’s syndrome), all following a unilateral parietal lesion, were found in the literature and were analyzed to test predictions from Braun’s “psychic tonus” model. As expected, patients with a positive syndrome had a right hemisphere lesion significantly more frequently, and those with a negative syndrome had a left hemisphere lesion significantly more frequently. Thus the psychic tonus model of hemispheric specialization, previously supported with regard to psychomotor baseline, libido, talkativeness, memory, auditory and visual perceptual tonus, now incorporates the tonus of representation of the body (body schema) in the parietal lobes.

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 lesions locus within the hemisphere, its size or its aetiology, presence of aphasic symptoms, psychiatric comorbidity, the patients age, gender, or hand preference, and several other potentially confounding variables.

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). It was also predicted that verbal ictal auditory hallucinations should result more often from left hemisphere foci, and non-verbal auditory ictal hallucinations from right hemisphere foci (test of hypothesis 2). Previously published cases (N=217) of ictal hallucination from a unilateral epileptic focus were reviewed and analyzed with multivariate statistics. Both predictions were strongly supported.

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.

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.