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Anjan Chatterjee

Publications and source records attributed to Anjan Chatterjee.

34 records · Page 2Linked to original sources
PubMed2004

Cosmetic neurology: the controversy over enhancing movement, mentation, and mood.

Advances in cognitive neuroscience and neuropharmacology are yielding exciting treatments for neurologic diseases. Many of these treatments are also likely to have uses for people without disease. Here, I review the ways in which medicine might make bodies and brains function better by modulating motor, cognitive, and affective systems. These potential "quality of life" interventions raise ethical concerns, some related to the individual and others related to society. Despite these concerns, I argue that major restraints on the development of cosmetic neurology are not likely. Neurologists and other clinicians are likely to encounter patient-consumers who view physicians as gatekeepers in their own pursuit of happiness.

Affect↗
PubMed2004

Sensory and response contributions to visual awareness in extinction.

Brain-damaged patients may extinguish contralesional stimuli when ipsilesional stimuli are presented simultaneously. Most theories of extinction postulate that stimuli compete for pathologically limited attentional resources with a bias to process ipsilesional over contralesional stimuli. Implicit in this view is the idea that responses follow the outcome of an earlier competition between inputs. In the current study of two patients, we used signal detection analyses to test the hypothesis that response criteria and response modalities also contribute to visual awareness. We found that identification was more sensitive than detection in uncovering deficits of contralesional awareness. Extinction was worse with bilateral stimuli when the ipsilesional stimulus was identical or similar to the target than when it was dissimilar. This diminished awareness was more likely to reflect a shift towards more conservative responses rather than diminished discrimination of contralesional stimuli. By contrast, one patient was better able to discriminate contralesional stimuli when using his contralesional limb to indicate awareness of targets than when using his ipsilesional limb. These data indicate that the nature of stimuli can modulate response criteria and the motor response can affect the sensory discriminability. Sensory discrimination and response output are not organized in a simple serial manner. Rather, input and output parameters interact in complicated ways to produce visual awareness. Visual awareness itself appears to be the outcome of two bottlenecks in processing, one having to do with sensory processing that may be covert and the other having to do with decision making, which by definition is overt. Finally, we advocate the use of signal detection analyses in studies of extinction, a method that has been surprisingly neglected in this line of research.

Awareness↗
PubMed2004

Evolution of epidemiologic methods and concepts in selected textbooks of the 20th century.

Textbooks are an expression of the state of development of a discipline at a given moment in time. By reviewing eight epidemiology textbooks published over the course of a century, we have attempted to trace the evolution of five epidemiologic concepts and methods: study design (cohort studies and case-control studies), confounding, bias, interaction and causal inference. Overall, these eight textbooks can be grouped into three generations. Greenwood (1935) and Hill (first edition 1937; version reviewed 1961)'s textbooks belong to the first generation, "early epidemiology", which comprise early definitions of bias and confounding. The second generation, "classic epidemiology", represented by the textbooks of Morris (first edition 1957; version reviewed 1964), MacMahon & Pugh (first edition 1960; version reviewed 1970), Susser (1973), and Lilienfeld & Lilienfeld (first edition 1976; version reviewed 1980), clarifies the properties of cohort and case-control study designs and the theory of disease causation. Miettinen (1985) and Rothman (1986)'s textbooks belong to a third generation, "modern epidemiology", presenting an integrated perspective on study designs and their measures of outcome, as well as distinguishing and formalizing the concepts of confounding and interaction. Our review demonstrates that epidemiology, as a scientific discipline, is in constant evolution and transformation. It is likely that new methodological tools, able to assess the complexity of the causes of human health, will be proposed in future generations of textbooks.

Epidemiologic Methods↗
PubMed2004

The neuropsychology of visual artistic production.

What happens to visual artists with neuropsychological deficits? This review will examine artistic production in individuals with a variety of syndromes including achromatopsia, neglect, visual agnosia, aphasia, epilepsy, migraine, dementia and autism. From this review it appears that artists are not spared visual-motor deficits despite their special graphic abilities. Rather their talents allow them to express visual deficits with particular eloquence. By contrast, the effects of aphasia on art are variable. In addition to deficits, neuropsychological syndromes may be associated with positive phenomena. Such phenomena induced by epilepsy or migraines can serve to inspire artists. This review also makes clear that artists with neuropsychological deficits do not necessarily produce art of lesser quality. Rather, their art may change in content or in style, sometimes in surprising and aesthetically pleasing ways. The neuropsychology of visual art also touches on a few central questions about the nature of artistic expression itself. For example, what forms can artistic representations take? How are visual features used descriptively and expressively? What roles do knowing and seeing play in depiction?

Adult↗
PubMed2004

Spatial-temporal anisometries following right parietal damage.

Patients with right parietal damage often have a lateralized deficit of spatial attention. In addition to a spatial deficit, such patients have also been reported to have a non-spatial deficit in temporal processing. Here, we tested the hypothesis that these spatial and temporal deficits might be linked if the right temporal-parietal cortex is important in integrating spatial and temporal attention. In AF, a patient with an acute right temporal-parietal stroke, we replicated previous observations showing that he was biased to judge ipsilesional stimuli as occurring before contralesional stimuli. More importantly, for vertically aligned stimuli, AF more accurately judged the temporal order of successive ipsilesional than contralesional stimuli. Furthermore, his contralesional performance improved with stimuli with larger vertical separations. Taken together, these findings provide additional evidence that right temporal-parietal damage produces a processing refractory period for stimuli in contralesional space that extends in both space and time. These findings are in agreement with other studies that suggest that the right temporal-parietal cortex is important in integrating the where and when of stimuli.

Adult↗
PubMed2003

Evidence for a unimodal somatosensory attention system.

Extinction is generally viewed as a disorder of selective attention for spatial locations. Recent physiologic, behavioral and lesion studies view spatial locations as a complex construct in which multiple modalities and motor systems are integrated. Accordingly, cross-modal and sensory-motor conditions often modify extinction. In a patient with tactile extinction, we tested the hypothesis that attentional deficits can also be confined to a specific sensory modality. Using objectively and subjectively balanced tactile stimuli and signal detection analysis, we found that our patient's contralesional tactile discrimination was not modulated by proprioceptive or visual input or by movement. By contrast, increasing the salience of the contralesional tactile stimuli did improve her contralesional tactile discrimination, consistent with our hypothesis that she suffered from a modality-specific attentional deficit. Additionally, she did not have any evidence of visual extinction, again bolstering our claim that her extinction was confined to touch. These data suggest that in addition to polymodal and sensory-motor attentional systems, spatial attention also operates on specific sensations. We also advocate the use of signal detection analysis, a method that has been surprisingly neglected in extinction research.

Aged↗
PubMed2003

Tetrabenazine in the treatment of severe pediatric chorea.

Tetrabenazine (TBZ) is widely used to treat adults with hyperkinetic movement disorders; however, published experience with the drug in pediatric patients is limited. We report on 5 children with severe chorea who were treated with TBZ. TBZ effectively controlled chorea in 4 patients, and despite the need for relatively high doses, it was well tolerated.

Anti-Dyskinesia Agents↗
PubMed2003

Acquired mirror writing and reading: evidence for reflected graphemic representations.

Mirror writing occurs when individual letters and whole word strings are produced in reverse direction. By analogy, mirror reading refers to the preference to read mirror reversed over normally written words. These phenomena appear rarely after brain damage and offer insight into the nervous system's organization of visual-spatial and visual-motor representations. We present the case of a 51-year-old patient with persistent mirror writing and reading following traumatic brain injury. She preferred to write in the mirror direction with either hand. She drew asymmetric pictures with the same directional bias as normal right-handed subjects, and she did not exhibit left-right confusion regarding other pictures. By contrast, on picture-word matching and lexical decision tasks, she was faster and more accurate with mirrored than normally written words. This pattern of performance suggests that her behavior was not accounted for by reflected motor programs, or by the mirroring of visual-spatial representations in general. Rather, we suggest that her behavior was produced by privileged access to mirrored graphemes. Furthermore, because she seemed better able to read irregular words in mirrored than in normal formats, we suggest that mirrored representations may exist at the whole word level and not simply at the letter level.

Brain Injuries↗
PubMed2003

Depression with anosognosia following a left subcortical stroke.

Controversy exists about whether depression following stroke represents a biologically mediated change or a psychological reaction to the deficits. We present a patient with an acute isolated personality change and depression following a lacunar infarct of the left internal capsule, who was unaware of his affective change. His anosognosia for the depression, which was abrupt and not accompanied by cognitive impairments, suggests that post stroke depression, at least in this case, is better explained by a biological than a psychological model.

Aged↗
PubMed2002

Neural substrates of action event knowledge.

Human concepts can be roughly divided into entities (prototypically referred to in language by nouns) and events (prototypically referred to in language by verbs). While much work in cognitive neuroscience has investigated how the brain represents different categories of entities, less attention has been given to the more basic distinction between entities and events. We used functional magnetic resonance imaging to examine brain activity while subjects performed a conceptual matching task that required them to access knowledge of objects and actions, using either pictures or words. Since action events involve movement through space, we hypothesized that accessing knowledge of actions would cause greater activation in brain regions involved in motion or spatial processing. In comparison to objects, accessing knowledge of actions through pictures was accompanied by increased activity bilaterally in the human MT/MST and nearby regions of the lateral temporal cortex. Accessing knowledge of actions through words activated areas just anterior and dorsal to area MT/MST on the left, within the posterior aspect of the middle and superior temporal gyri. We propose that the lateral occipital-temporal cortex contains a mosaic of neural regions that processes different kinds of motion, ranging from the perception of objects moving in the world to the conception of movement implied in action verbs. The lateral occipital-temporal cortex mediates the perceptual and conceptual features of action events, similar to the way that the ventral occipital-temporal cortex processes the perceptual and conceptual features of entities.

Adult↗
PubMed2002

Levetiracetam in the treatment of paroxysmal kinesiogenic choreoathetosis.

Anticonvulsants are frequently used in the treatment of paroxysmal kinesiogenic choreoathetosis (PKC). Although they are often extremely effective in eliminating paroxysmal movements, short- and long-term side-effects may limit their use in young patients. Levetiracetam (Keppra), a novel antiepileptic drug approved for the treatment of partial seizures is well tolerated in patients with epilepsy. We report on the use of levetiracetam in the treatment of PKC. Levetiracetam was effective in eliminating paroxysmal events and should be considered as an alternative to standard antiepileptic medications in this disorder.

Adult↗
PubMed2002

Influence of reference frames on asymmetries in Troxler's effect.

In 1804, Troxier discovered that, when an observer fixates on a point in central vision and attends to a peripheral stationary stimulus, the peripheral stimulus eventually fades from awareness. This phenomenon is known as Troxler's effect and is allegedly influenced by spatial attention. Asymmetries in Troxler's effect along horizontal and vertical meridian were a recent discovery. However, viewer- and environment-centered reference frames were aligned in prior studies, making it impossible to assess whether asymmetries correspond to viewer- versus environment-centered coordinate systems. This study was undertaken to (a) replicate the asymmetries in the upright condition among 39 participants without health issues and (b) use the asymmetrics to test contrasting predictions made by viewer- and environment-centered coordinate systems when they are decoupled using an experimental head-tilt condition. The horizontal and vertical asymmetries were replicated and consistent with a viewer-centered rather than an environment-centered reference frame.

Adolescent↗