Gazzaniga (Ed.) Cambridge, Mass.: MIT Press, 1995. Michael Gazzaniga has put in a tremendous amount of effort into promoting and shaping the emerging field of cognitive neuroscience. He has made important contributions, both in terms of his own research (e.g., Gazzaniga, 1989) and as the editor in chief of.

1 Cognitive Neuroscience: Brain Mechanisms of Memory and Cognition Rudolf N. Cardinal NST II Neuroscience (M5) / Psychology 2004 Lecture 2 (Monday 19 January) Motion processing; spatial cognition; parietal cortex Objectives Last time we considered the ventral visual stream; today, we will focus on the visuospatial aspects of processing carried out by the dorsal stream. We will consider how the techniques and findings of cognitive neuroscience can be used to investigate the psychological nature and neural basis of neurological syndromes such as neglect. Ikusa Megami Zero Sound Collection In A Megaphone. Basic Number Screening Test Manual For Driver. We will also consider different kinds of spatial processing, and how they might be mediated by the parietal cortex. Armed with this background, we will consider Goo- dale & Milner’s (1992) visual streams hypothesis. Anatomy, electrophysiology, and functional imaging of the dorsal stream Last lecture, we mentioned distinctions between the processing pathways arising from M and P retinal ganglion cells. Much useful information about visual motion derives from M-type retinal ganglion cells, which have high contrast sensitivity, transient responses, and little wavelength selectivity.

They project via the magno- cellular layer of the LGN, V1, and V2, to area V5 (also known as MT in the mon- key). This is sometimes referred to as the magnocellular-dominated stream. How- ever, we should note at this point that there is not a simple correspondence between the tuning of neurons to lower-level dimensions (such as the P versus M distinction) and higher-level visual processing. Information from P and M systems contributes in several ways to both dorsal and ventral streams, even if the M system dominates in the dorsal stream (see figures below). Two views of convergence and divergence in visual processing streams (MD magnocellular-dominated; ID interblob- dominated; BD blob-dominated). It remains true that the dorsal stream is magnocellular-dominated (as suggested by the left-hand figure, from last week’s handout), but that is not to say that the P-type retinal ganglion cells do not con- tribute to the dorsal stream at all. Xara Xtreme Pro 5 Serial Number. Left based on DeYoe & van Essen (1988); right from van Essen & DeYoe (1995).

In MT, neurons appear to respond quite selectively to movement and stereoscopic depth. Excitotoxic lesions of MT impair monkeys’ ability to saccade to a moving, but not a stationary target (Newsome et al., 1985), and a patient has been discovered who has a fairly discrete deficit in visual motion perception (akinetopsia) following damage to V5 (Zihl et al., 1983; Shipp et al., 1994). As we discussed in the last lec- ture, functional imaging studies have shown that V5 is consistently activated by vis- ual motion (e.g. Zeki et al., 1991). 4 parietal cortex (area 5) have a greater impact on somatosensory spatial processing than lesions of more posterior/inferior regions (area 7), which affect visuospatial cognition more. Spatial frames of reference Before proceeding further, we need to define some terms commonly used to de- scribe different spatial frames of reference (Behrmann, 2000). Our perception and movements are governed by a number of different frames of reference: we possess retinotopic, somatotopic, and tonotopic maps of sensory environments; these must be related to proprioceptive and motor information about our eye, head, and limb position.

How are these maps matched up? There are obvious difficulties given that the maps are spatially distorted (e.g. The size of somatosensory representations in somatosensory cortex depend on skin receptor density rather than the physical size of the represented area), the receptors are constantly moving, and the coordinate systems for these maps are very different. One solution would be to translate these into a common system of egocentric space that took account of different magnifications and distortions in sensory maps, and compensated for the constant movement of sensory receptors.