Helen Anderson, University of Witwatersrand
Journal of Consciousness Studies, 20, No. 3-4, pp. 6-32
This study can be taken as yet another argument against the twentieth century orthodoxy that language was the sole basis of consciousness, and that it ran on the equivalent of a classical computer, best left undisturbed by other inputs such as emotions. Instead the research discussed here suggests a complex interrelation between vision, emotion and language.
An early section of this paper discusses the neural basis of drawing abilities. Drawing involves both the left and right parietal lobes. The parietal lobes are involved with responses to the environment. The anterior parietal lobe relates to somatosensory sensations, such as touch, pain, temperature and proprioception, which is the sense of the relative position and effort exerted in different parts of the body. The posterior parietal lobe integrates somatosensory signals with visual, auditory and spatial orientation inputs. The region also selects and generates speech output.
In a 2003 study, drawing was also found to activate the posterior inferior temporal cortex and the ventral premotor area. The posterior inferior temporal is involved in writing, the generation of visual images, and the retrieval of images from long-term memory. The region lies on the border of the visual and the language brain regions, and can be involved in activation between the visual and the linguistic. Vision and language areas and the memory are all seen to be involved in drawing. The ventral premotor connects the visual and somatosensory regions with the motor area, particularly involving visual guidance and hand movements.
Research suggests that signals passing between the ventral premotor and posterior inferior temporal go via an area known as the arcuate fasciculus (AF). This is a group of white matter fibres connecting the temporal, frontal and parietal cortex, and this structure is more developed in primates than other mammals, and differently arranged in humans as compared to chimpanzees. In particular, it connects the Broca speech production area to the Wernicke speech comprehension area.
However, the AF is more extensive than that, with connections running between the frontal and temporal lobes and the amygdala. It is possible that the AF is the only direct connection between the frontal and the occipital regions. This link connects the executive functions with the primary visual processing area. On the basis of these studies, drawing is indicated to depend on regions in the frontal, temporal and occipital lobes that are connected by the AF.
The different development of this area in humans as against chimpanzees is suggested to be an evolutionary development related to the appearance of language in humans. It is suggested that there was a gradual evolutionary change rather than either a sudden mutation or merely a consequence of increased brain size. Music is suggested as a possible bridge between gesture and language, and studies indicate that music training can enhance the processing of meaning, speech production and emotional responses, manifesting as increased activity in the superior temporal sulcus. This brain region is associated with language, theory of mind and emotional information, suggesting a link between language and emotional processing. This is taken to suggest that language evolved in line with increased socialisation of human groups.
An area of white fibres, which is next to the arcuate fasciculus in humans but not chimpanzees, the inferior longitudinal fasciculus, connects the primary visual area with the amygdala and the hippocampus. Yet another white fibre structure, the uncinate fasciculus, connects the anterior temporal and the orbitofrontal, an important area for emotional processing, and this may be relevant in giving the language system a connection between the temporal and the emotion-related frontal regions.
Drawing can be performed in the absence of the AF, but these representations lack emotional meaning for a subject. Interconnectivity is required for an emotional response. Language and cognition are both seen as being embedded in emotional responses. Emotion is thus seen here as an essential support for the reasoning process.
Tags: anterior parietal lobe, Helen Anderson, inferior temporal cortex Posted by