The Psychology of Visual Art Eye, Brain and Art

Introduction

The outermost surface of the human brain is covered by a thin sheet of neurones called the neocortex or cerebral cortex. The sheet fits inside the skull only because of its extensive folds, rather like an umbrella furled up inside a case. The cerebral cortex is only 3 mm thick but has a total surface area of over 2 m2 when unfolded and contains about ten thousand million (billion) brain cells. It covers the brain like the shell of a nut, or the bark of a tree (cortex means bark or shell in Latin). The cortex is larger in humans than in any other species and is thought to endow us with uniquely human attributes.

The brain is divided vertically front-to-back into two hemispheres, one on each side of the head, which are interconnected by a massive band of nerve fibres called the corpus callosum. Anatomists subdivide each half of the cerebral cortex into four lobes, named as the frontal, parietal, temporal and occipital lobes after the bones that lie above them (Figure 3.1). The frontal lobe is at the front of the head behind your forehead, and the occipital lobe is at the back. The parietal and temporal lobes occupy the territory at the side and top of your head. A key feature of the cortex is specialisation of function. Like a medieval town in which different trades gather in different neighbourhoods – spice merchants here, money lenders there – small, circumscribed regions of the cortex specialise in serving particular mental functions. About one-fifth of the cortical surface is devoted to primary sensations (vision, sound, touch, balance, smell and taste) and to movement control. The rear-most part of the occipital cortex, known as the primary visual cortex (V1), receives input from the eyes and is responsible for vision, while a narrow strip of the cortex running side-to-side over the head from ear to ear receives sensory input from the body surface and mediates our perception of touch. Outside of these primary sensory areas, the remaining four-fifths of the cortex specialises in secondary cognitive functions. Research has shown that each lobe performs a specific set of tasks.