Intact recognition of facial emotion in Parkinson's disease.

Although the basal ganglia have been shown to be critical for the expression of emotion in prosody and facial expressions, it is unclear whether they are also critical for recognition of emotions. Selective pathology of parts of the basal ganglia is a hallmark of individuals with Parkinson's disease, and such patients have been examined in several studies of emotion. We examined 18 patients with Parkinson's disease (11 men, 7 women) and 13 age-, education-, gender ratio-, and IQ-matched normal controls on their ability to recognize emotions signaled by facial expressions. Parkinson's patients performed entirely normally on a quantitative task of recognizing emotional facial expressions. The findings do not support the notion that the sectors of basal ganglia that are dysfunctional in Parkinson's disease are essential for recognizing emotion in facial expressions.

Impaired declarative memory for emotional material following bilateral amygdala damage in humans.

Everyday experience suggests that highly emotional events are often the most memorable, an observation supported by psychological and pharmacological studies in humans. Although studies in animals have shown that nondeclarative emotional memory (behaviors associated with emotional situations) may be impaired by lesions of the amygdala, little is known about the neural underpinnings of emotional memory in humans, especially in regard to declarative memory (memory for facts that can be assessed verbally). We investigated the declarative memory of two rare patients with selective bilateral amygdala damage. Both subjects showed impairments in long-term declarative memory for emotionally arousing material. The data support the hypothesis that the human amygdala normally enhances acquisition of declarative knowledge regarding emotionally arousing stimuli.

Flavor and the frontal cortex.

Rats were trained to discriminate an aqueous compound of an odor and taste (amyl acetate and NaCl) from the components of the compound before removal of one olfactory bulb and the contralateral ventrolateral frontal cortex. In postoperative tests, experimental rats performed much more poorly than nonlesioned controls or controls which had all lesions made in the same hemisphere. However, there were no significant differences among groups on tests for detection of amyl acetate and NaCl. These results provide evidence that integration of taste and smell in the production of flavor occurs in the ventrolateral frontal cortex.

The ontogeny of a neurotoxic lesion in rat brain revealed by combined MRI and histology.

We have used magnetic resonance imaging (MRI) of the living rat brain to longitudinally analyze the ontogenesis of an ibotenic acid lesion targeted at the piriform cortex. The MRI data were systematically compared with data obtained from a battery of histopathological techniques, including Nissl stain, hematoxylin stain, and a stain for cytochrome oxidase activity. Two days after the lesioning, widespread and heterogeneous damage was detected in, around and distant from the toxin-targeted area. Some damage apparently diminished within approximately 10 days, whereas other damage remained throughout the length of this study (60 days). We found that the small-animal MRI technology used by us is useful in determining the initial, transient impact of surgery and neurotoxic lesioning, and in delineating the gross effects of the lesion over time. This is particularly useful for early elimination of animals from the protocol of physiological and behavioral experiments in which the lesion exceeds the target area. Our data also indicate that, in order to avoid confounding effects of transient post-lesioning phenomena, behavioral and physiological tests should be carried out in neurotoxically lesioned animals > 2 weeks after infliction of the lesion.

Modulation of protein tyrosine phosphorylation in rat insular cortex after conditioned taste aversion training.

Protein tyrosine phosphorylation is a major signal transduction pathway involved in cellular metabolism, growth, and differentiation. Recent data indicate that tyrosine phosphorylation also plays a role in neuronal plasticity. We are using conditioned taste aversion, a fast and robust associative learning paradigm subserved among other brain areas by the insular cortex, to investigate molecular correlates of learning and memory in the rat cortex. In conditioned taste aversion, rats learn to associate a novel taste (e.g., saccharin) with delayed poisoning (e.g., by LiCl injection). Here we report that after conditioned taste aversion training, there is a rapid and marked increase in tyrosine phosphorylation of a set of proteins in the insular cortex but not in other brain areas. A major protein so modulated, of 180 kDa, is abundant in a membrane fraction and remains modulated for more than an hour after training. Exposure of the rats to the novel taste alone results in only a small modulation of the aforementioned proteins whereas administration of the malaise-inducing agent per se has no effect. To the best of our knowledge, this is the first demonstration of modulation of protein tyrosine phosphorylation in the brain after a behavioral experience.

The role of serotonin in analgesia elicited by morphine in the periaqueductal gray matter (PAG).

The serotonergic antagonist, methysergide, administered into the periaqueductal gray matter (PAG), inhibited the antinociceptive effect of morphine, but not of glutamate, also administered into the PAG. At this dose methysergide did not alter the pain threshold when administered by itself. The implications for serotonin's role in the modulation of nociception in the PAG are discussed.