Biomedical subjects

Lisa T Eyler Zorrilla

Publications and source records attributed to Lisa T Eyler Zorrilla.

5 recordsLinked to original sources

PubMed2004

Functional brain asymmetries during visuomotor tracking.

This study examined brain asymmetries elicited during visuomotor tracking. Thirty-two healthy participants performed a fixed gaze, dynamic, pinch force, visuomotor tracking task during a functional magnetic resonance imaging study. The dynamic task required the subject to press a rubber bulb with the thumb to trace a cosine square wave varying in force amplitude from 0-500 cN and having a frequency of 1.5 Hz. Response hand order and direction of the stimulus presentation (right-to-left or left-to-right) were permuted across participants. Two forms of functional cerebral asymmetry were observed, hemispheric specialization and homologous lateralized response. The superior portion of the right middle frontal gyrus and the left supplementary motor area appeared specialized for VM tracking regardless of response hand used or stimulus movement direction. Lateralized effects appeared in the primary sensorimotor hand area, putamen, parietal operculum/posterior insula, dentate nucleus of the cerebellum, precuneus, and middle occipital gyrus. These lateralized areas of activation surfaced when either response hand or direction of stimulus movement was manipulated. The VM task used in this study activated asymmetrical neural activity in the vertically organized skelotomotor system and in sensory systems involving visual attention or proprioception.

Adult↗

PubMed2003

Functional abnormalities of medial temporal cortex during novel picture learning among patients with chronic schizophrenia.

BACKGROUND: Learning deficits are prominent among patients with chronic schizophrenia and are associated with poor everyday functioning. Little is known, however, about the brain physiology underlying these difficulties with encoding new information. PURPOSE: The purpose of the current study was to compare the brain response during novel picture encoding between patients with chronic schizophrenia and healthy individuals using functional magnetic resonance imaging (fMRI). METHODS: Nine middle-aged patients with DSM-III-R or DSM-IV schizophrenia and 10 age- and education-comparable healthy individuals were studied. Using fMRI, the blood oxygenation level dependent (BOLD) signal was measured during novel picture encoding (experimental condition) and during presentation of a repeated picture (control condition). Encoding-related brain response was examined in both groups and compared between the patient and comparison groups in each voxel within four bilateral search regions (fusiform gyrus, parahippocampal gyrus, hippocampus, and inferior frontal gyrus). RESULTS: Despite comparable subsequent ability to recognize the presented pictures, patients with schizophrenia showed abnormal encoding-related brain response in regions of the hippocampus and parahippocampal and fusiform gyrii compared to healthy individuals. In medial temporal regions, patients showed greater BOLD response during the control condition (repeated picture) than during the experimental condition (novel pictures). CONCLUSION: Abnormalities of the medial temporal brain systems examined in this study may underlie learning deficits in schizophrenia. Further research is needed to illuminate the role of these brain dysfunctions in poor everyday functioning and their amenability to treatment.

Chronic Disease↗

PubMed2003

BOLD and perfusion response to finger-thumb apposition after acetazolamide administration: differential relationship to global perfusion.

The authors studied the effects of altering global cerebral blood flow on both blood oxygen level-dependent (BOLD) response and perfusion response to finger-thumb apposition. A PICORE/QUIPSS II protocol was used to collect interleaved BOLD-weighted and perfusion-weighted images on eight finger-thumb apposition trials. Subjects were studied on a drug-free day and on a day when acetazolamide was administered between the second and third trials. After acetazolamide administration, resting cortical perfusion increased an average of 20% from preadministration levels, whereas the BOLD response to finger-thumb apposition decreased by an average of 35% in the S1M1 hand area. Contrary to predictions from the exhausted cerebrovascular reserve hypothesis and the oxygen limitation model, an effect of acetazolamide on cerebral blood flow response in the S1M1 hand area was not observed. Across the acetazolamide trials, BOLD response was inversely correlated with resting cortical perfusion for individual subject data. These results suggest that resting perfusion affects the magnitude of the BOLD response and is thus an important confounding factor in fMRI studies, and that the physiologic systems that increase cerebral blood flow in response to acetazolamide administration and systems that increase cerebral blood flow in response to altered neural activity appear to have additive effects.

Acetazolamide↗

PubMed2002

Increased amygdala activation to angry and contemptuous faces in generalized social phobia.

BACKGROUND: Generalized social phobia (GSP) is characterized by fear of social interactions and sensitivity to disapproval by others. Given the established role of the amygdala as part of a distributed neural system for the processing of emotional cues, we hypothesized that subjects with GSP would exhibit greater amygdala activation in response to harsh (angry, fearful, and contemptous) vs accepting (happy) facial emotional expressions compared with healthy control subjects (HCs). METHODS: Fifteen subjects with DSM-IV GSP and 15 age-, sex-, handedness-, and education-matched HCs, free of psychotropic medication for at least 12 weeks, viewed 60 color photographs from a standardized set of human facial stimuli, during which the task was to identify the sex of the person in the photograph. Data were collected across 3 functional (echo-planar) runs using a Siemens 1.5-T magnet, and analyzed using Analysis of Functional Neuroimaging software (Medical College of Wisconsin, Milwaukee). RESULTS: In the left allocortex (including the amygdala, uncus, and parahippocampal gyrus), subjects with GSP produced a significantly greater percent blood oxygen level-dependent signal change than did HCs for contemptous compared with happy faces (GSP: 0.72% vs HC: -0.01%; F(1,29) = 9.56, P =.004, Cohen d = 1.15) and for angry compared with happy faces (GSP: 0.45% vs HC: -0.09%; F(1,29) = 6.78, P =.02, Cohen d = 1.00). Subjects with GSP and HCs did not produce a statistically different percent signal change for fearful or nonexpressive faces compared with the happy faces in this region. CONCLUSIONS: These findings are consistent with a role for differential amygdala (and associated limbic) functioning in GSP. The pronounced response to contemptuous and angry facial expressions suggests that the amygdala in GSP may be particularly active in the processing of disorder-salient stimuli.

Adult↗

PubMedDate not supplied

Functional MRI and novel picture-learning among older patients with chronic schizophrenia: abnormal correlations between recognition memory and medial temporal brain response.

The relationship between disordered brain function and learning deficits in chronic schizophrenia is unclear. The authors compared correlations of brain response to picture encoding with subsequent recognition memory between samples of clinically stable patients over age 45 with schizophrenia and demographically similar healthy individuals. Subjects were studied with functional magnetic resonance imaging during novel picture encoding and a control condition. Comparison subjects showed an inverse relationship between subsequent recognition memory and brain response in medial temporal areas. Among schizophrenia patients, brain response in these regions was positively correlated with recognition memory. Brain-behavior relationships during learning were thus found to be qualitatively different between schizophrenic patients and healthy subjects.

Aged↗