Summary Sensory systems do not work in isolation; instead they show interactions that are specifically uncovered during sensory loss. To identify and characterize these interactions, we investigated whether visual deprivation leads to functional enhancement in primary auditory cortex (A1). We compared sound-evoked responses of A1 neurons in visually-deprived animals to those from normally-reared animals. Here we show that visual deprivation leads to improved frequency selectivity as well as increased frequency and intensity discrimination performance of A1 neurons. Furthermore, we demonstrate in vitro that in adults, visual deprivation strengthens thalamocortical (TC-) synapses in A1, but not in primary visual cortex (V1). Because deafening potentiated TC-synapses in V1 but not A1, cross-modal TC-potentiation seems to be a general property of adult cortex. Our results suggest that adults retain the capability for cross-modal changes while such capability is absent within a sensory modality. Thus multimodal training paradigms might be beneficial in sensory processing disorders.

Face perception in both humans and monkeys is thought to depend on neurons clustered in discrete, specialized brain regions. Because primates are frequently called upon to recognize and remember new individuals, the neuronal representation of faces in the brain might be expected to change over time. The functional properties of neurons in behaving animals are typically assessed over time periods ranging from minutes to hours, which amounts to a snapshot compared to a lifespan of a neuron. It therefore remains unclear how neuronal properties observed on a given day predict that same neuron's activity months or years later. Here we show that the macaque inferotemporal cortex contains face-selective cells that show virtually no change in their patterns of visual responses over time periods as long as one year. Using chronically implanted microwire electrodes guided by functional MRI targeting, we obtained distinct profiles of selectivity for face and nonface stimuli that served as fingerprints for individual neurons in the anterior fundus (AF) face patch within the superior temporal sulcus. Longitudinal tracking over a series of daily recording sessions revealed that face-selective neurons maintain consistent visual response profiles across months-long time spans despite the influence of ongoing daily experience. We propose that neurons in the AF face patch are specialized for aspects of face perception that demand stability as opposed to plasticity.vision | fMRI | physiology M any biological systems perform in a stable manner over time. The consistent behavior that is evident at the global level of the organism can persist despite continuous change in the system's component parts. A cup of coffee, for instance, tastes the same today as it did one year ago, despite the fact that the receptors in our taste buds are replaced every two weeks (1). In addition to the continuous replacement of individual cells, the protein constituents of cells likewise undergo nearly continuous turnover (2). What happens in the central nervous system? Because the lifespan of most neurons in the brain approaches that of the organism (3), it is conceivable that the population of faceselective cells that fire today when you see your mother, for instance, is identical to the population that fired under the same circumstances 10 years ago. However, in the absence of direct evidence, there is no reason to assume that this is the case, or more generally that stable network performance implies stable units. And indeed, both theoretical (4) and experimental results from motor cortex (5, 6) demonstrate that a network composed of unstable units may nonetheless exhibit stable performance. Recent recordings from the mouse hippocampus showed that reliable location signaling is driven largely by neurons that gradually enter and leave the population of functionally active place cells over the course of several days (7). In that study, only 15% of longitudinally monitored neurons were found to retain the same place fields in two sessions that were separ...

Introduction-The human multi-drug resistance gene (MDR1, ABCB1) codes for P-glycoprotein (P-gp), an important membrane-bound efflux transporter known to confer anti-cancer drug resistance as well as affect the pharmacokinetics of many drugs and xenobiotics. A number of single nucleotide polymorphisms (SNPs) have been identified throughout the ABCB1 gene which may have an effect on P-gp expression levels and function. Haplotype as well as genotype analysis of SNPs is becoming increasingly important in identifying genetic variants underlying susceptibility to human disease. Three SNPs, 1236C>T, 2677G>T, and 3435C>T have been repeatedly shown to predict changes in the function of P-gp. The frequencies with which these polymorphisms exist in a population have also been shown to be ethnically related.