Biomedical subjects

Sarah C Johnson

Publications and source records attributed to Sarah C Johnson.

3 recordsLinked to original sources

PubMed2006

Unirhinal olfactory function in schizophrenia patients and first-degree relatives.

Previous studies report birhinal impairments in odor identification in patients with schizophrenia and their family members. The authors employed unirhinal odor identification and detection threshold sensitivity tests in schizophrenia patients, healthy first-degree family members, and healthy comparison subjects. Patients and family members showed deficits in odor identification performance in both nostrils. Odor detection thresholds differed only between patients and healthy comparison subjects. Comparable odor identification deficits in both patients and healthy family members suggest that odor identification measures may serve as a sensitive endophenotypic vulnerability marker and that unirhinal olfactory measures are as precise, if not more so, than birhinal performance measures.

Adult↗

PubMed2005

Global-local visual processing in schizophrenia: evidence for an early visual processing deficit.

BACKGROUND: Abnormalities in early-stage visual processing might contribute to observed higher neurocognitive deficits in schizophrenia, but to date no clear link has been established. Schizophrenia has been associated with deficits in the magnocellular visual pathway, suggesting a relative bias for processing elemental (local) as opposed to configural (global) aspects of a hierarchical stimulus; however, global-local paradigm studies in schizophrenia have yielded mixed results. METHODS: In the current study, global-local and event-related potential (ERP) procedures were concomitantly used to assess temporal and spatial characteristics of hierarchical visual stimulus processing abnormalities. RESULTS: Patients (n = 24) had slower and less accurate responses to global stimuli than a healthy comparison group (n = 29). They exhibited a marked decrement in N150 ERP amplitude, which correlated with speed of response to global stimuli. They also failed to show an augmented P300 response to local stimuli. CONCLUSIONS: Behavioral and physiological data are consistent and support a global visual processing deficit in schizophrenia. This is manifest at a relatively early stage of visual processing and might relate to physiological disturbances in areas V3/V3a of the extrastriate cortex.

Adolescent↗

PubMed2003

Physiologic impairment of olfactory stimulus processing in schizophrenia.

BACKGROUND: Behavioral studies of olfaction have demonstrated impairments in the ability to detect and identify odors in patients with schizophrenia. These deficits appear to be independent of either symptom severity or other cognitive impairment. Only limited efforts have been made to investigate the neurophysiologic substrate of these olfactory abnormalities. This article reports the first examination of olfactory electrophysiologic responses in patients with schizophrenia. METHODS: Olfactory event-related potential responses to three different concentrations of hydrogen sulfide were recorded in a sample of 21 patients and 20 healthy control subjects. Odors were presented via an olfactometer to ensure there was no associated trigeminal nerve stimulation. RESULTS: Patients exhibited abnormalities in the amplitudes of the N1 and P2 components of the olfactory evoked potential, and delayed latency of the P2. The N1 abnormality, which denotes primary olfactory cortex activity, was related to impaired odor detection threshold sensitivity; the P2 abnormality was related to impaired odor identification. CONCLUSIONS: These data indicate the presence of a primary physiologic impairment in the olfactory cortex underlying behavioral olfactory deficits seen in patients with schizophrenia. This is consistent with postmortem and in vitro studies suggesting abnormalities in olfactory receptor neurons. Understanding the nature of these physiologic olfactory impairments could offer clues to the basic neuropathology of this disorder.

Adolescent↗