Biomedical subjects

Joscelyn E Fisher

Publications and source records attributed to Joscelyn E Fisher.

5 recordsLinked to original sources

PubMed2006

Semantic associations, lateralized frontal function, and context maintenance in schizotypy.

Symptom heterogeneity within conventional diagnostic groups is fostering a growing focus on narrower symptom profiles to identify psychological and biological mechanisms in psychopathology. Positive symptoms of schizophrenia are associated with context maintenance deficits, which in turn have been linked to frontal-lobe function. Frontal- and temporal-lobe brain dysfunction is also well documented in schizophrenia. The present study (N=36) examined how context and memory deficits are associated with subclinical symptoms in schizotypy by investigating the relationship between symptom reports, neuropsychological performance, and several facets of recognition memory. Context maintenance was probed via lures suggested by presented verbal material. Frontal brain function and positive symptom schizotypy predicted accuracy for lures, whereas posterior brain function and low positive affect predicted accuracy for distracters. This pattern of findings establishes continuity in disruption of context maintenance in clinical and subclinical populations.

Adolescent↗

PubMed2005

Neural mechanisms of affective interference in schizotypy.

Negatively valenced stimuli foster cognitive impairment in schizotypy and schizophrenia. To identify relevant brain mechanisms, the authors had 16 positive-schizotypy and 16 control participants perform an emotional Stroop task, judging the ink color of negative and neutral words during functional magnetic resonance imaging (fMRI) of regional brain activity. Schizotypy individuals showed increased right and decreased left activity in dorsolateral prefrontal cortex, indicating a deficit in maintenance of attentional set in the presence of negative emotional distractors. They also showed abnormal activity in ventral limbic areas, including decreased activity in nucleus accumbens and increased activity in hippocampus and amygdala, a circuit involved in the integration of cognitive and affective processes. These results indicate that aspects of emotion-cognition processes and the brain mechanisms that implement them are similar in schizotypy and schizophrenia.

Adult↗

PubMed2005

Emotion-modulated performance and activity in left dorsolateral prefrontal cortex.

Functional MRI (fMRI) was used to examine the relationship between processing of pleasant and unpleasant stimuli and activity in prefrontal cortex. Twenty volunteers identified the colors in which pleasant, neutral, and unpleasant words were printed. Pleasant words prompted more activity bilaterally in dorsolateral prefrontal cortex (DLPFC) than did unpleasant words. In addition, pleasant words prompted more activity in left than in right DLPFC. Response speed to pleasant words was correlated with DLPFC activity. These data directly link positive affect, enhanced performance, and prefrontal activity, providing some of the first fMRI evidence supporting models of emotional valence and frontal brain asymmetry based on electroencephalography (EEG).

Adult↗

PubMed2004

Lack of false recognition in schizophrenia: a consequence of poor memory?

The tendency to falsely recognize items as ones previously presented is increased in patients with frontal lesions and in older participants, whereas patients with medial temporal lobe damage may display such poor memory that they are not especially susceptible to false recognition. Since patients with schizophrenia are often compared to these groups neurocognitively, we explored the extent to which they are more susceptible to false memory. Participants were presented with word lists along a semantic theme, such as "bread". After list presentation, recognition tasks were administered which contained both the studied words as well as unstudied words. Some of the unstudied words were related to the theme of the previously studied words, but never actually presented (e.g. semantic "lures"). In a separate test, free recall of these lists of words was assessed. Interestingly, it was control participants who made more errors at recall, and were especially susceptible to intrusions of the semantic lures. Patients with schizophrenia did not make more false recognition errors in general, and surprisingly they made disproportionately fewer false recognition errors to semantic lures specifically. We conclude that despite poor memory, patients with schizophrenia are not especially susceptible to interference from previous tasks and are not particularly prone to false recollections.

Adult↗

PubMed2003

Probed recall for serial order deficits in short-term memory in schizophrenic patients.

BACKGROUND: Patients with schizophrenia frequently display problems in tasks demanding working memory. In a previous study, we examined short-term memory (STM) for serial order by having participants recall lists of letters from the first item to the last item in the order in which they were presented, and we examined the types of errors made (e.g., omissions, intrusions and movements; [Neuropsychology 15 (2001) 128]). We found that the disproportionate errors schizophrenic patients made were omissions at the end of six-item lists, a finding we suggested might reflect patients' longer output times, which adds to information maintenance demands. If this is the case, we predicted that the group difference in the terminal positions could be eliminated through the use of a probed recall paradigm. METHOD: In the current study, 26 schizophrenic patients and 33 control participants were tested on a probed recall task that was similar to our previous serial recall task except that instead of recalling the whole sequence of letters, participants were probed as to which letter appeared in a specific position in the sequence. RESULTS: We found that when participants were probed for later positions, recall was equivalent in the groups (i.e., recency), but disproportionately worse in patients for earlier positions. CONCLUSIONS: We suggest that schizophrenic patients' limited STM span for serial order is not attributable to a selective deficit in memory for serial order. Rather, we propose that it may be explicable in terms of impaired information maintenance and thus this becomes evident in conditions involving longer sequences of stimuli.

Adult↗