The role of precuneus and left inferior frontal cortex during source memory episodic retrieval

The posterior medial parietal cortex and left prefrontal cortex (PFC) have both been implicated in the recollection of past episodes. In a previous study, we found the posterior precuneus and left lateral inferior frontal cortex to be activated during episodic source memory retrieval. This study further examines the role of posterior precuneal and left prefrontal activation during episodic source memory retrieval using a similar source memory paradigm but with longer latency between encoding and retrieval. Our results suggest that both the precuneus and the left inferior PFC are important for regeneration of rich episodic contextual associations and that the precuneus activates in tandem with the left inferior PFC during correct source retrieval. Further, results suggest that the left ventro-lateral frontal region/frontal operculum is involved in searching for task-relevant information (BA 47) and subsequent monitoring or scrutiny (BA 44/45) while regions in the dorsal inferior frontal cortex are important for information selection (BA 45/46).     

Cerebral activation during thermal stimulation of patients who have burning mouth disorder: an fMRI study

The pathophysiology of burning mouth disorder (BMD) is not clearly understood, but central neuropathic mechanisms are thought to be involved. The aim of this study was to gain insight into the pathophysiology associated with BMD by using functional magnetic resonance imaging (fMRI). Areas of brain activation following thermal stimulation of the trigeminal nerve of eight female patients with BMD (mean age 49.1+/-10.1) were mapped using fMRI and compared with those of eight matched pain-free volunteers (mean age 50.3+/-12.3). Qualitative and quantitative differences in brain activation patterns between the two study groups were demonstrated. BMD patients displayed greater fractional signal changes in the right anterior cingulate cortex (BA 32/24) and bilateral precuneus than did controls (p<0.005). The control group showed larger fractional signal changes in the bilateral thalamus, right middle frontal gyrus, right pre-central gyrus, left lingual gyrus, and cerebellum than did the BMD patients (p<0.005). In addition, BMD patients had less volumetric activation throughout the entire brain compared to the control group. Overall, BMD patients displayed brain activation patterns similar to those of patients with other neuropathic pain conditions and appear to process thermal painful stimulation to the trigeminal nerve qualitatively and quantitatively different than pain-free individuals. These findings suggest that brain hypoactivity may be an important feature in the pathophysiology of BMD.     

Uncovering putative neural markers of risk avoidance

Risk avoidance is a hallmark of psychopathological conditions such as anxiety disorders. Yet few studies have examined its neural basis. The present work sought to identify the neural correlates of risk avoidance. While functional MRI scans were acquired, healthy adults (N = 23) played a Wheel of Fortune game during which they chose to bet or pass on each of 104 proposed gamble trials. Participants also completed the Cognitive Appraisal of Risky Events (CARE, Fromme et al., 1997), a self-report measure of “real world” risky behavior. As expected, decision-making was associated with activation, as measured by increased BOLD responses, of the striatum, insula, anterior cingulate cortex, dorsolateral prefrontal cortex, and parietal lobe. Risk avoidance during probabilistic trials (percent of trials passed) was significantly correlated with precuneus and striatal responses to trials with a certain outcome (No-Risk). Similarly, “real world” risk avoidance, as measured by the CARE, was significantly correlated with precuneus activity during No-Risk trials. Collectively, these data suggest that precuneus and striatal responses to decision-making under certainty represent putative neural markers of risk avoidance in the laboratory and in the “real world.” Further, they underline the need to extend neuroimaging research on risk avoidance, and associated anxiety disorders, to posterior cortical regions.     

Cortical Activations during judgments about the self and an other person

Self-related thought and other person related thought have received a great deal of study in recent years, but have seldom been examined in the same experiment. This study used functional magnetic resonance imaging (fMRI) to compare the neural correlates of judgments of ones own preferences with judgments of another person's preferences. Each participant viewed food names and made one of three decisions: self (whether he or she liked the food); other (whether a specific friend liked the food), or letter (whether there were more than two vowels in the food name). Self and other decisions both activated bilateral medial areas of the frontal and parietal lobes and the bilateral insula in comparison to the letter task. Self activated superior medial parietal areas in comparison to other, whereas other led to greater activation in inferior medial parietal and left lateral frontal areas than self. These results indicate that the neural networks underlying self processing and other person processing may share common neural substrates, particularly regions associated with representation of the body and mental states.     

l-DOPA changes ventral striatum recruitment during motor sequence learning in Parkinson's disease

Recent research indicates that longstanding temporal lobe epilepsy (TLE) is associated with extratemporal, i.e. parietal cortex damage. We investigated egocentric and allocentric memory by use of first-person large-scale virtual reality environments in patients with TLE. We expected that TLE patients with parietal cortex damage were impaired in the egocentric memory task. Twenty-two TLE patients with hippocampal sclerosis (HS) and 22 TLE patients without HS were compared with 42 healthy matched controls on two virtual reality tasks affording to learn a virtual park (allocentric memory) and a virtual maze (egocentric memory). Participants further received a neuropsychological investigation and MRI volumetry at the time of the assessment. When compared with controls, TLE patients with HS had significantly reduced size of the ipsilateral and contralateral somatosensory cortex (postcentral gyrus). When compared with controls or TLE patients without HS, TLE patients with HS were severely impaired learning the virtual maze. Considering all participants, smaller volumes of the left-sided postcentral gyrus were related to worse performance on the virtual maze. It is concluded that the paradigm of egocentric navigation and learning in first-person large-scale virtual environments may be a suitable tool to indicate significant extratemporal damage in individuals with TLE.     

School sport—A neurophysiological approach

The aim of this study was to identify neurophysiological correlates for previously reported positive effects of exercise on academic achievement in school children using a distributed source localization algorithm. Electro-cortical activity of 11 school children (9–10y) was recorded before and after a moderate 15-min bike exercise. Data were analyzed using standardized low resolution brain electromagnetic tomography (sLORETA) in the alpha (7.5–12.5 Hz) and beta (12.5–35 Hz) frequency range. We were able to show a significant increase in alpha activity post-exercise, which could be localized in the precuneus. Moreover a distinct decrease in beta activity could be noticed post-exercise in left temporal areas including Wernicke's area. We propose that apart from health-promoting aspects school sport serves a second even more important challenge. On a central level a well observed overall state of physical relaxation after exercise is reflected by a more synchronized state in the precuneus. We speculate this to be responsible for an increase in concentrativeness and cognitive function post-exercise. Moreover a previously reported increase in academic achievement post-exercise could be directly linked to exercise induced neuroplasticity in regions that are relevant for language processing.