Biomedical subjects

Jonathan K Wynn

Publications and source records attributed to Jonathan K Wynn.

7 recordsLinked to original sources

PubMed2006

Exploring the short term visual store in schizophrenia using the attentional blink.

Schizophrenia patients exhibit numerous deficits on visual processing tasks, ranging from very early stages of visual processing (e.g., backward masking) to the later working memory stages (e.g., delayed match-to-sample, N-back). However, little is known about deficits in an intermediate stage of visual information processing, namely short term visual memory (STVM). The attentional blink (AB) paradigm is considered to be a valid way to assess the STVM, and recent studies have reported AB deficits in schizophrenia. However, it is not clear whether the reported AB deficit in schizophrenia patients is due to their increased susceptibility to backward masking or increased vulnerability in the STVM. In this study we first found poorer performance in the AB task in 37 schizophrenia patients compared to 26 normal controls. To examine the effects of increasing and decreasing mask strength on AB performance in patients and controls, we next systematically varied the masking effect by varying the length of the distracters immediately following the targets. The manipulation had relatively little effect on the patient--control differences and patients continued to show an enhanced AB effect across conditions. The findings suggest that the enhanced AB effect in schizophrenia reflects an abnormality in their short term visual memory, as opposed to their enhanced susceptibility to visual masking.

Adult↗

PubMed2006

An analysis of categorical perception of facial emotion in schizophrenia.

BACKGROUND: Emotion perception deficits have been extensively documented in schizophrenia and are associated with poor social functioning. Yet fundamental questions about the nature and scope of these impairments remain unanswered from commonly used experimental tasks. An alternative categorical perception paradigm that focuses on distinguishing boundaries between emotions was used to evaluate whether schizophrenia patients demonstrate atypical patterns of categorical perception and a negativity bias in the identification of ambiguous facial expressions. METHOD: 47 schizophrenia outpatients and 31 nonpsychiatric controls completed a forced-choice emotion identification task. Stimuli consisted of a series of digitized facial images that were morphed in 10% signal intensity increments along continua between pairs of emotions (happy-sad; fearful-happy; angry-fearful; angry-sad) and presented in a random order. For each emotion continuum, measures of the response slope and the location of the boundary shift point between emotions were calculated for each group. RESULTS: The schizophrenia group demonstrated significantly shallower response curves than controls across all emotion continua. Despite these generally less precise demarcations between emotions, patients did not significantly differ from controls in the location of the shift point between emotions on any of the continua. CONCLUSIONS: Schizophrenia patients demonstrated impaired categorical perception of facial expressions with generally less sharp categorizations of ambiguous stimuli to one emotion category or another. However, patients did not demonstrate a negativity bias in their processing of ambiguous facial expressions. The emotional continuum paradigm can help to clarify the nature and boundaries of affect perception deficits in schizophrenia.

Adolescent↗

PubMed2006

Quantitative EEG and low resolution electromagnetic tomography (LORETA) imaging of patients with persistent auditory hallucinations.

Electrophysiological studies have demonstrated gamma and beta frequency oscillations in response to auditory stimuli. The purpose of this study was to test whether auditory hallucinations (AH) in schizophrenia patients reflect abnormalities in gamma and beta frequency oscillations and to investigate source generators of these abnormalities. This theory was tested using quantitative electroencephalography (qEEG) and low-resolution electromagnetic tomography (LORETA) source imaging. Twenty-five schizophrenia patients with treatment refractory AH, lasting for at least 2 years, and 23 schizophrenia patients with non-AH (N-AH) in the past 2 years were recruited for the study. Spectral analysis of the qEEG and source imaging of frequency bands of artifact-free 30 s epochs were examined during rest. AH patients showed significantly increased beta 1 and beta 2 frequency amplitude compared with N-AH patients. Gamma and beta (2 and 3) frequencies were significantly correlated in AH but not in N-AH patients. Source imaging revealed significantly increased beta (1 and 2) activity in the left inferior parietal lobule and the left medial frontal gyrus in AH versus N-AH patients. These results imply that AH is reflecting increased beta frequency oscillations with neural generators localized in speech-related areas.

Adult↗

PubMed2005

Sensorimotor gating, orienting and social perception in schizophrenia.

Basic neurocognition and social cognition appear to influence the social impairments of persons with schizophrenia. This study examined relationships between two very basic automatic processes (i.e., sensorimotor gating and orienting) and social perception in schizophrenic patients. Thirty outpatients with schizophrenia completed psychophysiological measures of sensorimotor gating (prepulse inhibition, PPI), orienting (prepulse facilitation, PPF), and social perception (the Half Profile of Nonverbal Sensitivity, Half PONS). A median split was used to divide patients into poor and good gaters and poor and good orienters. Analyses revealed that patients with good PPI scored significantly higher on the Half PONS than patients with poor PPI. PPI showed a significant correlation (r=-0.54) with Half PONS performance, indicating that schizophrenia patients who were better able to gate out competing stimuli (i.e., less startle) were also better at detecting relevant social cues. Orienting (PPF) and social perception were not related. This study is the first to our knowledge to demonstrate an association between sensorimotor gating and social perception. The findings are consistent with other studies that have demonstrated relationships between basic neurocognition and social cognition. By showing a link between sensorimotor gating and social perception, this study supports social cognition's potential role as a mediator of the relationship between neurocognition and social functioning in schizophrenia.

Adult↗

PubMed2005

Event-related gamma activity in schizophrenia patients during a visual backward-masking task.

OBJECTIVE: Schizophrenia patients experience deficits in many aspects of cognition and perception. Abnormalities in gamma activity may underlie some of these deficits, including rapid processing of visual stimuli. This study examined event-related gamma range activity during a visual backward-masking task in schizophrenia patients and normal comparison subjects. METHOD: Event-related gamma activity was recorded in 15 normal comparison subjects and 32 schizophrenia patients. Participants had event-related gamma activity recorded while viewing 60 unmasked visual targets and 240 trials of visual backward masking. Effects of group, accuracy (correct versus incorrect), stimulus-onset asynchrony, and regional activity (left versus right hemisphere, anterior versus posterior regions) were assessed. RESULTS: Schizophrenia patients had significantly reduced gamma activity in relation to comparison subjects during the backward-masking task. Normal comparison subjects showed significantly greater gamma activity in the right hemisphere, whereas schizophrenia patients did not show this pattern of lateralization. For the unmasked target, there was no group effect and no significant interactions in gamma-band responses. CONCLUSIONS: These results extend previous findings of abnormal gamma range activity in schizophrenia patients. Patients showed overall less gamma activity and failed to show lateralization of activity to the right hemisphere during masking, but they showed comparable levels of gamma activity to unmasked stimuli. Schizophrenia patients' poorer performance during a masking task may be partly influenced by this abnormal level and the distribution of gamma activity.

Adult↗

PubMed2004

Prepulse facilitation and prepulse inhibition in schizophrenia patients and their unaffected siblings.

BACKGROUND: Deficits in schizophrenia patients and their first-degree relatives have been reported in prepulse inhibition (PPI), a phenomenon that measures an early stage of information processing (sensorimotor gating). It is less clear whether these information processing deficits extend to prepulse facilitation (PPF), which measures a later stage of generalized alerting or orienting. METHODS: This study examined three separate issues: first, whether schizophrenia patients have deficits in PPI and PPF; second, whether the siblings of patients show deficits in these processes; and third, whether prepulse duration influences the degree of the deficits. These issues were examined in 76 schizophrenia patients, 36 of their siblings, and 41 normal control subjects. RESULTS: Patients and siblings did not differ from control subjects in PPI, perhaps due to the use of different procedural parameters compared with other laboratories that have consistently found PPI deficits in schizophrenia patients. Patients and their siblings produced significantly less PPF than control subjects. For both PPI and PPF, prepulse duration was not a significant factor. CONCLUSIONS: These results imply that PPF deficits reveal a generalized alerting or orienting deficit that is present in both schizophrenia patients and their siblings, suggesting that this deficit may be tapping an endophenotypic vulnerability factor.

Acoustic Stimulation↗

PubMed2004

The functional relationship between visual backward masking and prepulse inhibition.

This experiment demonstrated a relationship between prepulse inhibition (PPI) of the startle eyeblink and visual backward masking in college students. It was hypothesized that recovery from backward masking effects is due in part to sensory gating, as assessed by auditory and visual PPI. Visual presentations of letters served as targets or visual prepulses in an intermixed session of backward masking and PPI. Backward masking and PPI (both auditory and visual) were assessed at stimulus onset asynchronies of 30, 45, 60, 120, and 150 ms. A repeated-measures regression revealed that there was a relationship between backward masking and PPI for both visual and auditory PPI, with higher levels of PPI being associated with greater recovery from backward masking. The data are consistent with the hypothesis that recovery from backward masking effects is affected by sensory gating acting in part to gate out the interruptive effects of the mask.

Acoustic Stimulation↗