Neural Science and Vision – Part 11

Next up is Chapter 52 on Learning and Memory, authored by the seemingly law-firm sounding trio of Shohamy, Schacter and Wagner. Dan Schacter may be the best recognized of the three, having written a book on the seven sins of memory for popular consumption which was an outgrowth of an article on the subject published in the American Psychologist, as well as a video on true vs. false memories featuring Alan Alda of M*A*S*H notoriety.

About a year or two ago, if memory serves correct, Patty Lemer queried me about the extent to which vision was involved in executive function. Her motivation for doing so was that so-called executive function disorder had emerged over the past decade as an attractive box into which many individuals with learning difficulties were being placed. Entire schools, such as the Franklin Academy, began hitching their identity to the way in which they handled executive function (EF). The implication was that since vision resides in the occipital lobe in the posterior part of the brain, the frontal lobe was responsible for attention and therefore had nothing to do with vision – a very narrow viewpoint. I told her at the time that vision was intimately involved with EF if, for no other reason, we merely focused on the role of the frontal eye fields (FEF) in selective attention.

After reading Chapter 52, I would have been even more pointed in my response, factoring in the role of working memory. The authors write: “In humans, working memory consists of at least two subsystems – one for verbal information and another for visuospatial information. The functioning of these two subsystems is coordinated by a third system called the executive control processes. Executive control processes are thought to allocate attentional resources to the verbal and visuospatial subsystems and to monitor, manipulate, and update stored representations. The visuospatial subsystem of working memory retains mental images of visual objects and of the location of objects in space. The rehearsal of spatial and object information is thought to involve modulation of this information in the parietal, inferior temporal, and occipital cortices by the frontal and premotor cortices.”

Ah … the pervasiveness of vision throughout the brain.

Various forms of implicit memory subserve our daily routines. These include the learning of habits and motor, perceptual, and cognitive skills, and the formation and expression of conditioned responses. Generally speaking these forms of implicit memory are characterized by incremental learning, which proceeds gradually with repetition and aided in many instances by reinforcement and reward.

Research has shown that visual perception and memory are the most important components of vision processing in the brain. It was thought that the perceptual aspect of a visual stimulus occurs in visual cortical areas and that this serves as the substrate for the formation of visual memory in a distinct part of the brain called the medial temporal lobe (MT). However, current evidence indicates that there is no functional separation of areas. Entire visual cortical pathways and connecting medial temporal lobe are important for both perception and visual memory.  The relationship between MT and vision is so intimate that it has a dual label of MT/V5 – the middle ground between the dorsal visual pathway above and the ventral visual stream below.

The medial temporal lobes are thought to be involved in several kinds of incremental learning. For example, implicit learning of regularities between visual cues is called statistical learning. This is essential to how learning takes place through repetition. Skill learning moves from a cognitive stage, where knowledge is represented explicitly, and the learner must pay a great deal of attention to performance, to an autonomous stage where the skill can be executed with a minimum of conscious attention. In essence, the learning of sensorimotor skills depends on numerous brain regions that vary depending on the specific associations being learned.

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