Parvathy Vijeesh

Cognition in the Brain: The Anatomy and Mechanisms of the Brain • The nervous system is the basis for our ability to perceive, adapt to, and interact with the world around us (Gazzaniga, 1995, 2000; Gazzaniga, Ivry, & Mangun, 1998). • Through this system we receive, process, and then respond to information from the environment (Pinker, 1997a; Rugg, 1997). Gross Anatomy of the Brain: Forebrain,Midbrain, Hindbrain Initially, the forebrain is generally the farthest forward, toward what becomes the face. The midbrain is next in line. And the hindbrain is generally farthest from the forebrain, near the back of the neck [Figure 2.2 (a)]. In development, the relative orientations change so that the forebrain is almost a cap on top of the midbrain and hindbrain. Nonetheless, the terms still are used to designate areas of the fully developed brain. Figure 2.2 Fetal Brain Development. Over the course of embryonic and fetal development, the brain becomes more highly specialized and the locations and relative positions of the hindbrain, the midbrain, and the forebrain change from conception to term. Figure 2.3 Structures of the Brain. The forebrain, the midbrain, and the hindbrain contain structures that perform essential functions for survival and for high-level thinking and feeling The Forebrain • The forebrain is the region of the brain located toward the top and front of the brain. • It comprises the cerebral cortex, the basal ganglia, the limbic system, the thalamus, and the hypothalamus (Figure 2.3). • The cerebral cortex is the outer layer of the cerebral hemispheres. • It plays a vital role in our thinking and other mental processes. • The basal ganglia (singular: ganglion) are collections of neurons crucial to motor function. • Dysfunction of the basal ganglia can result in motor deficits. These deficits include tremors, involuntary movements, changes in posture and muscle tone, and slowness of movement. • Deficits are observed in Parkinson’s disease and Huntington’s disease. Both these diseases entail severe motor symptoms (Rockland, 2000; Lerner & Riley, 2008; Lewis & Barker, 2009). The limbic system is important to emotion, motivation, memory, and learning. Animals such as fish and reptiles, which have relatively undeveloped limbic systems, respond to the environment almost exclusively by instinct. Mammals and especially humans have relatively more developed limbic systems. Our limbic system allows us to suppress instinctive responses (e.g., the impulse to strike someone who accidentally causes us pain). Our limbic systems help us to adapt our behaviors flexibly in response to our changing environment. The limbic system comprises three central interconnected cerebral structures: the septum, the amygdala, and the hippocampus. Involved in learning, emotions, and motivation (in particular, the hippocampus influences learning and memory, the amygdala influences anger and aggression, and the septum influences anger and fear) Thalamus Primary relay station for sensory information coming into the brain; transmits information to the correct regions of the cerebral cortex through projection fibers that extend from the thalamus to specific regions of the cortex comprises several nuclei (groups of neurons) that receive specific kinds of sensory information and project that information to specific regions of the cerebral cortex, including four key nuclei for sensory information: (1) from the visual receptors, via optic nerves, to the visual cortex, permitting us to see; (2) from the auditory receptors, via auditory nerves, to the auditory cortex, permitting us to hear; (3) from sensory receptors in the somatic nervous system, to the primary somatosensory cortex, permitting us to sense pressure and pain; and (4) from the cerebellum (in the hindbrain) to the primary motor cortex, permitting us to sense physical balance and equilibrium Hypothalamus Controls the endocrine system; controls the autonomic nervous system, such as internal temperature regulation, appetite and thirst regulation, and other key functions; involved in regulation of behavior related to species survival (in particular, fighting, feeding, fleeing, and mating); plays a role in controlling consciousness (see reticular activating system); involved in emotions, pleasure, pain, and stress reactions. Midbrain • Superior colliculi (on to) Involved in vision (especially visual Reflex) • Inferior colliculi (below) Involved in hearing • Reticular activating system (also extends into the hindbrain) Important in controlling consciousness (sleep arousal), attention, cardiorespiratory function, and movement. • Gray matter, red nucleus, substantia nigra, ventral region Important in controlling movement Hindbrain Cerebellum -Essential to balance, coordination, and muscle tone Pons (also contains part of the RAS)-Involved in consciousness (sleep and arousal); bridges neural transmissions from one part of the brain to another; involved with facial nerves Medulla oblongata-Serves as juncture at which nerves cross from one side of the body to opposite side of the brain; involved in cardio respiratory function, digestion, and swallowing The outer shell of the brain is known as the cerebral cortex, and itis responsible for most of the higher cognitive processes. The various lobes of the cortex are extensively interconnected, so that a single cognitive process may involve many different cortical areas. However, the brain is to some extent ‘modular’ in that certain brain areas do perform specific functions. We know this largely from the study of brain lesions, since damage to a certain part of the brain can often cause quite specific impairments. In recent years the introduction of brain scanning equipment has provided an additional source of knowledge to supplement the findings of brain lesion studies.