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Biomedical subjects

Jennifer E McDowell

Publications and source records attributed to Jennifer E McDowell.

9 recordsLinked to original sources
PubMed2007

A cognitive neuroscience approach to studying the role of overconfidence in problem gambling.

Research on the neural correlates of decision making in gambling tasks may be informative for understanding problem gambling. The present study explored confidence and overconfidence using magnetoencephalography (MEG) to measure brain activity during a judgment task. Nineteen undergraduates who self-identified as frequent gamblers (average age 19.7 years; 5 females, 14 males) participated in this study. Participants first completed the DIGS (Winters, Specker & Stinchfield, 2002), a measure of gambling pathology. They then engaged in a behavioral task of confidence assessment, wherein they answered two-alternative trivia questions and estimated the probability that each answer was correct. In a subsequent MEG task, they viewed the questions and a target answer, and indicated with a button press whether the target matched the correct answer. Confidence was directly related to activity in the right prefrontal cortex. Matching and mismatching targets were associated with activity in the medial occipital cortex and left supramarginal gyrus, respectively. An interaction of pathology and match/mismatch was observed in the right inferior occipital-temporal junction region, showing more activity following a mismatch in non-problem gamblers, but not in problem gamblers. Implications of the results for understanding of top-down modulation and attentional systems are discussed in relation to gambling behavior.

Adult↗
PubMed2006

The neural correlates of habituation of response to startling tactile stimuli presented in a functional magnetic resonance imaging environment.

Functional magnetic resonance imaging (fMRI) provides a means of identifying neural circuitry associated with startle and its modulation in humans. Twelve subjects who demonstrated eyeblink startle in the laboratory were recruited for an fMRI study in which they were scanned while presented with two identical runs consisting of alternating blocks of no stimuli and startling tactile stimuli. Together, behavioral and imaging data are consistent with a pattern of general cortical and thalamic activation induced by startling stimuli that shows habituation both across and within runs. From Run 1 to Run 2, both the eyeblink amplitude and the fMRI signal decreased. Within Run 1, there was a graded decrease in eyeblink amplitude and whole-brain fMRI signal across blocks of startling stimuli. A similar graded decrease was observed in the thalamus signal, as well. Thus, startling tactile stimuli initially induce widespread cortical and thalamic activity, perhaps mediated by the reticular activating system. The activity then habituates in a graded fashion with repeated presentations of the stimuli.

Adult↗
PubMed2006

Scotopic sensitivity in schizophrenia.

Among participants with schizophrenia there is evidence for early-stage visual processing deficits, which may arise in the rod pathways. Input to the earliest level of this pathway, however, has not been tested in this population. It has been widely hypothesized that schizophrenia participants have magnocellular deficits that occur at the pre-cortical level. To address this hypothesis, we studied absolute scotopic (dark-adapted) sensitivity in fifteen schizophrenia and fifteen matched control participants. Scotopic thresholds were assessed using a 1.85-deg, 510-nm circular test stimulus located at 10 degrees eccentricity in the left visual field and presented in Maxwellian-view. Thresholds were obtained using a two-alternative forced-choice paradigm (an average of 200 trials per participant was obtained). Threshold estimates were derived using probit analysis. In this procedure the transformed binomial data (the inverse of the normal probability integral) is fit with a weighted linear regression. Noise was defined as the average deviation from this line. Lens optical density was also assessed by comparing absolute scotopic thresholds to the extinction spectrum of rhodopsin. Scotopic thresholds and lens density values of the two groups were evaluated using independent samples t-tests. The scotopic thresholds, and associated noise, did not differ between the schizophrenia and control participants. Lens density was also nearly identical between groups. These results suggest that magnocellular deficits in schizophrenia may not be due to problems at the level of the rods but are more likely to occur later in the visual pathway.

Adult↗
PubMed2006

Basal ganglia-thalamocortical circuitry disruptions in schizophrenia during delayed response tasks.

BACKGROUND: Schizophrenia is characterized by executive functioning deficits, presumably mediated by prefrontal cortex dysfunction. For example, schizophrenia participants show performance deficits on ocular motor delayed response (ODR) tasks, which require both inhibition and spatial working memory for correct performance. METHODS: The present functional magnetic resonance imaging (fMRI) study compared neural activity of 14 schizophrenia and 14 normal participants while they performed ODR tasks. RESULTS: Schizophrenia participants generated: 1) more trials with anticipatory saccades (saccades made during the delay period), 2) memory saccades with longer latencies, and 3) memory saccades of decreased accuracy. Increased blood oxygenation level-dependent (BOLD) signal changes were observed in both groups in ocular motor circuitry (e.g., supplementary eye fields [SEF], lateral frontal eye fields [FEF], inferior parietal lobule [IPL], cuneus, and precuneus). The normal, but not the schizophrenia, group demonstrated BOLD signal changes in dorsolateral prefrontal regions (right Brodmann area [BA] 9 and bilateral BA 10), medial FEF, insula, thalamus, and basal ganglia. Correlations between percentage of anticipatory saccade trials and BOLD signal changes were more similar between groups for subcortical regions and less similar for cortical regions. CONCLUSIONS: These results suggest that executive functioning deficits in schizophrenia may be associated with dysfunction of the basal ganglia-thalamocortical circuitry, evidenced by decreased prefrontal cortex, basal ganglia, and thalamus activity in the schizophrenia group during ODR task performance.

Adult↗
PubMed2005

Electroencephalography/magnetoencephalography study of cortical activities preceding prosaccades and antisaccades.

The temporal and spatial characteristics of brain activity preceding prosaccades and antisaccades were investigated using source reconstructions of 64-channel electroencephalography and 148-channel magnetoencephalography data. Stimulus-locked data showed early cuneus activity was stronger during antisaccades, and later occipital gyrus activity was stronger preceding prosaccades, which suggests a top-down influence on early visual processing. Response-locked data showed that supplementary eye field, prefrontal cortex, and medial frontal eye field activity was greater for antisaccades than for prosaccades prior to saccade generation. Lateral frontal eye field activity appeared to be inhibited prior to antisaccade response generation. The spatial and temporal resolution of combined electroencephalography/magnetoencephalography data allows the evaluation of specific cortical activities preceding saccades and for demonstration of how activities differ as a function of response contingencies.

Adult↗
PubMed2004

Behavioral plasticity of antisaccade performance following daily practice.

The ability to change behavior to adapt to the environment, known as behavioral plasticity, is an important part of daily life. In the present study subjects' performances on antisaccade tasks were manipulated by training them on one of three different eye movement tasks (antisaccade, prosaccade, and fixation). Thirty subjects were tested at three time points over a 2-week period and practiced their assigned task every day between test sessions. Subjects who trained on antisaccades significantly decreased their error rates, while maintaining their reaction time, suggesting that accuracy did not improve at the expense of speed. Subjects who practiced the prosaccade task made more errors on the antisaccade task on subsequent test sessions, while those who practiced the fixation task showed no change across test sessions. These results suggest that deliberate practice of eye movement tasks can alter antisaccade performance, and that the direction of the effect is dependent upon the type of practice in which the subject engages.

Adolescent↗
PubMed2002

Neural correlates of refixation saccades and antisaccades in normal and schizophrenia subjects.

BACKGROUND: Schizophrenia subjects demonstrate difficulties on tasks requiring saccadic inhibition, despite normal refixation saccade performance. Saccadic inhibition is ostensibly mediated via prefrontal cortex and associated cortical/subcortical circuitry. The current study tests hypotheses about the neural substrates of normal and abnormal saccadic performance among subjects with schizophrenia. METHODS: Using functional magnetic resonance imaging, blood oxygenation level-dependent (BOLD) data were recorded while 13 normal and 14 schizophrenia subjects were engaged in refixation and antisaccade tasks. RESULTS: Schizophrenia subjects did not demonstrate the increased prefrontal cortex BOLD contrast during antisaccade performance that was apparent in the normal subjects. Schizophrenia subjects did, however, demonstrate normal BOLD contrast associated with refixation saccade performance in the frontal and supplementary eye fields, and posterior parietal cortex. CONCLUSIONS: Results from the current study support hypotheses of dysfunctional prefrontal cortex circuitry among schizophrenia subjects. Furthermore, this abnormality existed despite normal BOLD contrast observed during refixation saccade generation in the schizophrenia group.

Adult↗
PubMed2002

Neurobiological measures of schizotypal personality disorder: defining an inhibitory endophenotype?

OBJECTIVE: Subjects with schizotypal personality disorder demonstrate deficits in inhibition when assessed on prepulse inhibition, P50 suppression, and antisaccade paradigms. This study determined if distinct subgroups of subjects with schizotypal personality disorder could be identified on the basis of performance on these measures and whether endophenotypes could be defined for future genetic study by using measures of inhibitory function. METHOD: Prepulse inhibition, P50 suppression, and antisaccade paradigms were assessed in 21 subjects with schizotypal personality disorder. RESULTS: Seven subjects with schizotypal personality disorder had deficits on each paradigm; seven had no deficits on any paradigm. P50 and antisaccade deficits were present in five of the same subjects and significantly correlated. CONCLUSIONS: These results suggest that P50 and antisaccade performance reflects a common endophenotype and that prepulse inhibition identifies a separate endophenotype reflecting different neurobiological substrate(s) in subjects with schizotypal personality disorder. This pattern may generalize to schizophrenia spectrum disorder patients.

Acoustic Stimulation↗