CD44 is a novel molecular player that regulates structure and function of the synapse. It affects excitatory synaptic transmission, dendritic spine shape, number of functional synapses, and activity-dependent neuronal plasticity. These functions are exerted via the regulation of small Rho GTPases.

Local field potentials from different visual cortical areas and subdivisions of the cat's lateral posterior-pulvinar complex of the thalamus (LP-P) were recorded during a behavioral task based on delayed spatial discrimination of visual or auditory stimuli. During visual but not auditory attentive tasks, we observed an increase of ␤ activity (12-25 Hz) as calculated from signals recorded from the caudal part of the lateral zone of the LP-P (LPl-c) as well as from cortical areas 17 and 18 and the complex located at the middle suprasylvian sulcus (MSS). This ␤ activity appeared only in the trials that ended with a successful response, proving its relationship to the mechanism of visual attention. In contrast, no enhanced ␤ activity was observed in the rostral part of the lateral zone of the LP-P and in the pulvinar proper. Two subregions of LPl-c (ventromedial and dorsolateral) were distinguished by visually related, attentional ␤ activity of low (12-18 Hz) and high (18 -25 Hz) frequencies, respectively. At the same time, area 17 exhibited attentional activation in the whole ␤ range, and an increase of power in low-frequency ␤ was observed in the medial bank of MSS, whereas cortical area 18 and the lateral bank of the MSS were activated in the high ␤ range. Phase-correlation analysis revealed that two distinct corticothalamic systems were synchronized by the ␤ activity of different frequencies. One comprised of cortical area 17, ventromedial region of LPl-c, and medial MSS, the second involved area 18 and the dorsolateral LPl-c. Our observations suggest that LPl-c belongs to the wide corticothalamic attentional system, which is functionally segregated by distinct streams of ␤ activity.

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