Frontal lobes: twin orchestra conductors in cerebral symphony.

Abstract

The brain has two processors. Left hemisphere functions like a serial processor and right hemisphere like a parallel processor. Though the brain to body ratio in apes and human beings is nearly the same but intellect-wise there is a great difference. It is probably differentiation of two hemispheres in human beings which increase their mental capacity. The control of opposite in both hemispheres may be due to inverted image of eye lenses, representing upside down images in opposite hemispheres and reciprocal control over the threats in the visual field. The cerebral hemispheres are different structurally, functionally and chemically.1 Right hemispheric cortex is thicker than that of left and it has forward protrusion (Yakovlevian torque).2 Cytoarchitecture shows increased number of spindle cells on the right side. Goldberg mentioned that the association fibers in the right hemisphere are longer and have greater speed of processing. In contrast, the left hemisphere consists of short fibers with lower speed of processing. The ratio of noradrenaline and dopamine in both hemispheres also differs.3 Frontal lobes, the expressive and the most humane part of brain is the most recently evolved region, important for cognition flexibility, motivation and control of social and behavioral impulses. Consciousness in animals may be limited to one sense. Dogs are smell conscious. In snakes touch, vision and taste are independent of each other. Human beings are unique having consciousness of SELF and all the senses are linked together and sampled in frontal lobes creating whole body image in relation to atmosphere. Frontal lobes are the twin orchestra conductors in cerebral symphony. These have inhibitory effect over other parts of brain to concentrate or meditate. Frontal lobes work in an economized state at low energy level. It has a braking system for thinking, motor activity and feelings; and regulates emotions. Hippocampalprefrontal cortical circuits are important to working memory. Pre-frontal cortex is used during consciously thinking and holds information to understand, decide, recall and memorize. It integrates different information gathered from different areas of brain into purposeful and planned behavior, anticipating future, making critical judgment and discerns various ideas to fit. It has multimodal association cortex. The heteromodal component is known as granular cortex, whereas the paralimbic component is known as dysgranular cortex.4 It processes information from various sensory modalities and integrated here for memory, perception, and diverse cognitive processes. Pre-frontal cortex is the last cortical area which myelinates in adolescence.5 According to Jacksonian Principle,6 evolution is passage from the simple, the most automatic, towards the complex, the most voluntary or least automatic. Dissolution is the reverse process of evolution which passes from the most complex, the least automatic towards the most simple, and the most automatic. In other words, in disease those parts suffer first and most, which have the highest, the most complex, or those functions that have developed latest. So the frontal lobes are latest and highly complex in the development and the first to be knocked out. Frontal lobes have 3 areas with different functions namely the motor and pre-motor unit, the frontal eye field area and the pre-frontal cortex (PFC). The later is divided into medial frontal cingulated cortex, dorsolateral cortex and the orbital frontal lobe.