Changes In Prefrontal Cortex Activity Research Articles

Rapid plasticity in the prefrontal cortex during affective associative learning.

MultiCS conditioning is an affective associative learning paradigm, in which affective categories consist of many similar and complex stimuli. Comparing visual processing before and after learning, recent MultiCS conditioning studies using time-sensitive magnetoencephalography (MEG) revealed enhanced activation of prefrontal cortex (PFC) regions towards emotionally paired versus neutral stimuli already during short-latency processing stages (i.e., 50 to 80 ms after stimulus onset). The present study aimed at showing that this rapid differential activation develops as a function of the acquisition and not the extinction of the emotional meaning associated with affectively paired stimuli. MEG data of a MultiCS conditioning study were analyzed with respect to rapid changes in PFC activation towards aversively (electric shock) paired and unpaired faces that occurred during the learning of stimulus-reinforcer contingencies. Analyses revealed an increased PFC activation towards paired stimuli during 50 to 80 ms already during the acquisition of contingencies, which emerged after a single pairing with the electric shock. Corresponding changes in stimulus valence could be observed in ratings of hedonic valence, although participants did not seem to be aware of contingencies. These results suggest rapid formation and access of emotional stimulus meaning in the PFC as well as a great capacity for adaptive and highly resolving learning in the brain under challenging circumstances.

EPA-1047 – Short-term effects of antipsychotic treatment on prefrontal hemodynamic responses in first-episode schizophrenia during tower of london: A multi-channel nirs study

Planning ability as a critical component of executive function has been used to investigate prefrontal cortex (PFC) function in Schizophrenia patients by several neuroimaging studies. However, the changes of PFC activation after effective antipsychotic treatment are still unclear. The aim of this study is to explore whether there is any variation in the prefrontal hemodynamic response during Tower of London test after 6 weeks’ antipsychotic treatment in schizophrenia patients, and the relationship between the changes in PFC activation and some demographic factors as well as the severity of the patients’ psychiatric symptoms. 40 patients with first-episode schizophrenia were recruited for the present study. 28-channel NIRS (near infrared spectroscopy) was used to measure changes in hemoglobin concentration in the prefrontal cortical surface area during Tower of London (TOL) test—a classic neuropsychological test for planning abilities. The patients were examined before treatment and after six weeks’ treatment with second-generation antipsychotic medicines. After the short-term treatment, the patients’ TOL test performance and the activations in PFC during the task period did not differ from baseline (P>0.05), although the psychiatric symptoms of the patients were improved significantly(positive subscale score 18.25±2.86 & 12.75±2.60; general psychopathology 33.67±3.65 & 27.00±3.67; PANSS total score 72.25±7.07 & 55.42±7.53; P<0.001). It suggests that the impairment of cognitive function and the function of the PFC of schizophrenia patients would not be improved with the improvement of psychiatric symptoms, as further support the hypothesis that PFC damage is a durable impairment for schizophrenia.

Application of Near-infrared Spectroscopy in Ergonomics and Human Factors: A Discussion Panel

This panel presents near-infrared spectroscopy (NIRS) theory and its principles, and applicability of NIRS on a variety of muscle and cerebral regions during activities that demand considerable physical and mental effort. Five presentations will cover: (1) theoretical basis of NIRS; (2) NIRS-derived hemodynamic measurements in shoulder muscles during repetitive tasks; (3) development of NIRS for use in evaluating long term standing fatigue; (4) monitoring training-related changes in prefrontal cortex activation with functional NIRS; and (5) simultaneous evaluation of physical and mental work.

Bipolar depressed patients show both failure to activate and failure to de-activate during performance of a working memory task

BackgroundBipolar depression has been found to be associated with changes in prefrontal cortex activity during performance of cognitive tasks. However, the role of task-related de-activations has been little investigated. MethodForty-one bipolar depressed patients and 41 matched normal controls underwent fMRI scanning while performing baseline, 1-back and 2-back versions of the n-back task. Linear models were used to obtain maps of within-group activations and areas of differential activation between the groups. ResultsThe bipolar depressed patients showed reduced activation in the dorsolateral prefrontal cortex (DLPFC) bilaterally and several other regions. After controlling for differences in task performance only differences in the DLPFC and cerebellum remained. Left DLPFC activation was inversely correlated with Hamilton and MADRS scores. The patients showed failure to de-activate in the medial prefrontal cortex, an area corresponding to the anterior medial node of the default mode network. LimitationsTo confirm default mode network dysfunction demonstration of resting-state connectivity abnormalities would also be required. The study was carried out on treated patients, and did not assess for presence of depressive symptoms in the healthy controls. ConclusionsBoth prefrontal cortical and default mode network dysfunction appear to characterise bipolar depression. The former, but not the latter, is associated with symptom severity.

Age-related changes in prefrontal cortex activity are associated with behavioural deficits in both temporal and spatial context memory retrieval in older adults

Aging is associated with decrements in both spatial and temporal context retrieval. Functional neuroimaging studies of young adults suggest that there are differences in left versus right lateral prefrontal cortex (PFC) contributions to spatial versus temporal source (recency) retrieval, respectively. The goal of the current study was to determine if age-related decreases in temporal and spatial context retrieval are due to common or distinct changes in PFC function. To address this goal we conducted an event-related functional magnetic resonance imaging (fMRI) study in which young and older adults performed recognition, recency and spatial context retrieval tasks using face stimuli to identify event-related PFC regions associated with these retrieval tasks in both age groups. Our behavioural results indicated that older adults did not differ on recognition performance, but did exhibit a deficit in both context retrieval tasks, compared to young adults. The fMRI results suggest that age-related deficits in both spatial and temporal context retrieval may be linked to functional changes in right dorsolateral and left medial anterior PFC (APFC) function. In addition, based on brain-behaviour correlations in older adults, our results imply that older adults attempt to compensate for these deficits by engaging left dorsolateral PFC during spatial context retrieval and right APFC during temporal context retrieval.

Perceived Exertion is Not Necessarily Associated with Altered Brain Activity during Exercise

Previous studies have investigated the relationship between prefrontal cortex activation and perceived exertion during prolonged exercise. However, the effect of perceived exertion on prefrontal cortex activity is confounded by exercise intensity. Therefore, the changes in prefrontal cortex activity in response to perceived exertion remain unclear. The purpose of the present study was to investigate the relationship between the activation (oxygenation) of the prefrontal cortex and perceived exertion during constant work-rate elbow-flexion exercise with or without muscle-spindle stimulation. Ten healthy, right-handed subjects participated in the study. Near-infrared spectroscopy with probes positioned over the prefrontal cortex measured its activation throughout elbow-flexion exercise. Subjects performed sustained elbow-flexion exercise at 25-35% of the maximal voluntary contraction (MVC) with or without muscle-spindle stimulation (vibration), which can decrease perceived exertion. The ratings of perceived exertion were significantly lower during exercise with vibration (Ex-Vib) than during exercise without vibration (Ex) (p<0.05). The oxygenation of the prefrontal cortex during Ex-Vib did not significantly differ from that during Ex (p>0.05). These results indicated that perceived exertion was not necessarily associated with prefrontal cortex activation during exercise.

Prefrontal cortex and the organization of recent and remote memories: An alternative view

Prefrontal cortex and the organization of recent and remote memories: An alternative view

Reductive catalyst regeneration

Bipolar depression has been found to be associated with changes in prefrontal cortex activity during performance of cognitive tasks. However, the role of task-related de-activations has been little investigated.Forty-one bipolar depressed patients and 41 matched normal controls underwent fMRI scanning while performing baseline, 1-back and 2-back versions of the n-back task. Linear models were used to obtain maps of within-group activations and areas of differential activation between the groups.The bipolar depressed patients showed reduced activation in the dorsolateral prefrontal cortex (DLPFC) bilaterally and several other regions. After controlling for differences in task performance only differences in the DLPFC and cerebellum remained. Left DLPFC activation was inversely correlated with Hamilton and MADRS scores. The patients showed failure to de-activate in the medial prefrontal cortex, an area corresponding to the anterior medial node of the default mode network.To confirm default mode network dysfunction demonstration of resting-state connectivity abnormalities would also be required. The study was carried out on treated patients, and did not assess for presence of depressive symptoms in the healthy controls.Both prefrontal cortical and default mode network dysfunction appear to characterise bipolar depression. The former, but not the latter, is associated with symptom severity.

Electrical Stimulation of Rat Medial Prefrontal Cortex Enhances Forebrain Serotonin Output: Implications for Electroconvulsive Therapy and Transcranial Magnetic Stimulation in Depression

Decreased activity of the prefrontal cortex (PFC), as well as reduced serotonergic neurotransmission, is considered as a characteristic feature of major depression. The mechanism by which electroconvulsive therapy (ECT) and transcranial magnetic stimulation (TMS) achieve their antidepressant effects may involve changes in PFC activity. It is, however, still unclear whether these changes are accompanied by increased synaptic availability of serotonin (5-HT). In the present study, 5-HT efflux in the rat ventral hippocampus and amygdala was analyzed using in vivo microdialysis during low-current electrical stimulation of PFC and other cortical regions. Electrical stimulation of the medial PFC produced current-dependent increases in limbic 5-HT output in both urethane-anesthetized and behaving rats. No effects on 5-HT levels were seen after comparable stimulation of either the lateral parts of the PFC, the medial precentral area, the primary motor cortex or the parietal cortex. This pronounced regional specificity of the effect of medial PFC stimulation on limbic 5-HT output suggests that activation of this particular area might play a crucial role in such antidepressant treatments as ECT and TMS.