Biomedical subjects

A J Wintink

Publications and source records attributed to A J Wintink.

4 recordsLinked to original sources

PubMed2001

Hippocampal involvement in the expression of kindling-induced fear in rats.

Kindling dramatically increases fearful behavior in rats. Because kindling-induced fear increases in magnitude as rats receive more stimulations, kindling provides a superb opportunity to study the nature and neural mechanisms of fear sensitization. Interestingly, these changes in behavior are accompanied by increased binding to inhibitory receptors and decreased binding to excitatory receptors in the CA1 and dentate gyrus regions of the hippocampus. This led us to hypothesize that kindling-induced fear may result from an increased inhibitory tone within hippocampal circuits. To test this hypothesis, we investigated FOS protein immunoreactivity in hippocampal and amygdalar regions of kindled rats that were exposed to an unfamiliar open field. We found that FOS immunoreactivity was significantly decreased in the CA1 region, dentate gyrus, and perirhinal cortex of kindled rats compared to sham-stimulated rats. These results support our hypothesis that kindling-induced fear may be produced by inhibition within hippocampal circuits. They also suggest that neural changes within the hippocampus may be important for the sensitization of fear.

Amygdala↗

PubMed2001

P3 topographical change with task familiarization and task complexity.

The P3 event-related potential (ERP) component is usually reported as having a centro-parietal maximum. However, a more frontal P3 topography is also evident in early-session trials which may be masked by averaging over the entire session, and is also present longer in elderly subjects. This maintenance of hyperfrontal topography is interpreted as a sign of reduced prefrontal adaptive functioning. In the present study, P3 amplitude was examined in young adults to determine: (1) how early in the test session the reduction in hyperfrontality occurs; and (2) the effect of task complexity on the P3 amplitude across electrode sites (Fz, Cz, Pz). ERPs were elicited using a working memory n-back task. Single-trial ERP waveforms were averaged in successive blocks of five trials. There was a greater decrease in P3 amplitude at Fz compared to Cz and Pz sites after the first block, and the decrease reached an asymptote by the third block. The results are interpreted as indicating rapid decrease in initial P3 hyperfrontality for a simple task in young adults, and an increased ratio of P3 amplitude at frontal versus posterior sites in more complex tasks.

Adult↗

PubMedDate not supplied

The related roles of dopamine and glutamate in the initiation of 50-kHz ultrasonic calls in adult rats.

Effects of amphetamine on the production of 50-kHz ultrasonic calls were studied. Calls were emitted spontaneously or were induced by an intrahypothalamic-preoptic injection of glutamate. Sonographic analysis of recorded calls revealed that they were within the 35-70-kHz sound frequency range reported for the 50-kHz call type. Systemic amphetamine (AMPH, 2 mg/kg) significantly increased the number of spontaneously emitted 50-kHz calls and the effect of AMPH was dose-dependent. Low dose of intracerebral glutamate (17 microg) had no additive effect on the number of AMPH-induced calls. Higher dose of intracerebral glutamate alone (34 microg) significantly increased the number of 50-kHz calls, which was completely reversed by systemic application of haloperidol (2 mg/kg), a dopamine antagonist. The results suggest that glutamate-induced or spontaneously occurring 50-kHz calls in adult rats are dependent upon dopaminergic transmission. It is postulated that this type of calls may be indicative of dopamine mediated affective state in adult rats.

Aging↗

PubMedDate not supplied

Task complexity and habituation effects on frontal P300 topography.

The P3(00) event-related potential (ERP) component is usually reported as having a centroparietal maximum. However, the P3 topography is more frontal in early-session trials which may be masked by averaging over the entire session and is evident longer into the test session among elderly subjects. This hyperfrontality is interpreted as a sign of poor prefrontal adaptive functioning. In the present study, P3 amplitude was examined in university students to determine how early a change in amplitude would be evident and the effect of task complexity on the amplitude across electrode sites. ERPs were elicited using a working-memory n-back task where participants pressed a key to target letter presentations in three conditions of increasing complexity. Single-trial ERP waveforms were then averaged in successive sequences of five trials. Results revealed a greater decrease in frontal P3 amplitude compared to the central and parietal P3 after the first block of five target trials until the third block. The results are interpreted as indicating rapid decrease in hyperfrontality with habituation to an easy task. Increases in task complexity (the 2-back paradigm), however, reduced this frontal P3 attenuation. Results support a P3 ERP model of hyperfrontality reflecting short-term adaptive function by the prefrontal cortex.

Adult↗