Psyc 2240 - Biological Basis of Behaviour - Chapter 12 PDF

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Psyc 2240 - Biological Basis of Behaviour - Chapter 12 chapter 12: What causes emotional and motivated behaviour - Motivation: Behaviour that seems purposeful and goal directed. 12-1 Identifying the causes of behaviour - Rearing experiences must activate brain circuits that make us feel good. Behaviour for brain maintenance - Sensory deprivation (HEBB): Depriving people of nearly all sensory input. - Conclusion of this study is that the brain has an inherent need for stimulation. Neural circuits and behaviour - Androgens (male hormone) sexual activity in an example of a reward activity. - Another reward circuit comes from our chemical senses, smell or taste The Chemical sense - Olfaction - Our sense of smell Receptors for smell - Identifying chemo signals is similar to identifying other sensory stimuli (Light, sound and touch). - Scent interacts with chemical receptors. - The life of an olfactory receptor neuron is about 60 days. - Receptor surface for olfaction is the Olfactory Epithelium in the nasal cavity. - Each receptor cells sends a process ending in 10-20 cilia into a mucus layer, THE - Olfactory Mucosa: ➔ Chemicals in the air that we breathe dissolve in the mucosa to interact with the cilia. ➔ If an olfactory chemo signal affects the receptors, metabotropic activation of a specific G protein leads to an opening of NA channels and a change in membrane potential. Olfactory pathways - Olfactory receptors cells project to the olfactory bulb, ending in ball-like tufts of dendrites- The Glomeruli - where they form synapses with the dendrites of mitral cells. - Mitral cells send their axons from the olfactory bulb to the broad range of the forebrain. - Olfactory targets like the amygdala and pyriform cortex have no connections through the. - Thalamus: ➔ A thalamic connection does project to the orbitofrontal cortex (OFC) which receives projections from the thalamic nucleus.

Accessory olfactory system - Class of odorants = Pheromones; Biochemicals released by one animal that act like chemo signals and can affect the physiology or behaviour of another animal of the same species. - Pheromones are unique odours b/c they are detected by a specific olfactory receptor system, the Vomeronasal Organ, which is made up of small groups of sensory receptors connected by a duct to the nasal pathway. - Receptor cells in the vomeronasal organ send their axons to the accessory olfactory bulb. - Vomeronasal connects to the amygdala and hypothalamus which can play a role in reproductive and social behaviour. Human olfactory processing - Body odours also activate structures not previously believed to participate in olfactory processing, including the posterior cingulate cortex, occipital cortex, and anterior cingulate cortex- regions also activated by visually emotional stimuli. - Processing body odours is mostly unconscious. - Similar unconscious processes seem to occur during visual and auditory information processing and to play an important role in our emotional reactions. Receptors for tastes - Four most familiar tastes 1. oSweet 2. oSour 3. oSalty 4. oBitter - oUmami receptor which is very sensitive to glutamate, a neurotransmitter molecule. - Gustatory stimuli interact with the receptor tip, the microvilli, to open channels, leading to changes in membrane potential. - Taste buds contact the branches of afferent cranial nerves. Gustatory pathways - Cranial nerves 7,9, and 10 form the main gustatory nerve, The Solitary Tract. - On entering the brainstem, the tract splits. - One route travels through the posterior medulla to the vent posterior medial nucleus of the thalamus. ➔ This nucleus in turn sends out two pathways, one to the primary somatosensory cortex (S1). ➔ The other to the primary gustatory cortex of the insula (a region just rostral to the secondary somatosensory cortex (S2). - Gustatory region in the insula is dedicated to taste. - S1 : Is responsive to tactile information and is responsible for both localising tastes on the tongue and for our reactions to a food's texture.

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Gustatory cortex : Sends a projection to the orbital cortex in a region near the input from the olfactory cortex. Areas in the right orbital cortex : Mediate the pleasantness of taste, whereas the same region in the left mediates the unpleasantness of taste. The insula : Identifies the nature and intensity of flavours, the OFC evaluates the affective properties of taste.

Second Pathway - Gustatory nerve projects via the nucleus of the solitary tract in the brainstem, to the hypothalamus and amygdala. - These inputs somehow participate in feeding behaviour, possibly evaluating the pleasantness and strength of flavours.

Evolution, Environment and Behaviour Evolutionary influence on behaviour - Innate releasing mechanisms (IRMs) activators for inborn adaptive responses that aid an animal’s survival. - IRMs help an animal to feed, reproduce and escape predators. - IRMs are present from birth rather than acquired through experience. - The term rekasing indicates that IRMs act as triggers for behaviours set in motion by internal programs. - IRMs are prewired into the brain but experience can modify them. - Animals that survive long enough to reproduce and have healthy offspring are more likely to pass on their brain circuit genes than are animals with traits that make them less likely to survive and successfully reproduce. - Evolutionary psychology: The field that applies principles of natural selection to explanations of human behaviour. ➔ Evolutionary psychologists assume that any behaviours, including homicide, occur because natural selection has favoured the neural circuits that produce it. Environmental influences on behaviours - Learning as a cause of behaviour. - B.F Skinner believed that behaviours are selected by environmental factors. - Certain events function as rewards, or reinforce. - Reinforcement can be manipulated to encourage the display of complex behaviours. - Skinner argued that understanding a person’s reinfroment history could account for various phobias. ➔ He also argued against the commonly held view that much of human behaviour is under our own control. ➔ Free will is an illusion because behaviour is controlled not by the organism but rather the environment through experience. - Epigenetics changes regulate changes in memory circuits.

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Learned Taste Aversion: Is acquired even when the food eaten is in fact unrelated to the later illness. ➔ A curious aspect of taste aversion learning is that we are unaware of having formed the association until we encounter the taste and or smell again. The fact that the nervous system is often prewired to make certain associations but not to make ether has led to the concept of preparedness in learning theories.

Neuroanatomy of motivated and emotional behaviour - The neural circuits that control behaviour encompasses regions at all levels of the brain, but the critical neural structures in emotional and motivated behaviours are the hypothalamus and associated pituitary gland, the limbic system and the frontal lobe. - Emotional expression in all mammals is related to activity in the limbic system and frontal lobes. - The limbic and frontal regions project to the hypothalamus which houses many basic neural circuits for controlling behaviours and for autonomic processes that maintain critical body functions within a narrow-fixed range – Homeostatic Mechanisms. - To produce behaviour the hypothalamus sends axons to other brainstem circuits. - Many other routes to the brainstem and spinal cord bypass the hypothalamus, among them projections from the motor cortex to the brainstem and spinal cord. Regulatory and no regulatory behaviour Regulatory behaviours - Behaviours motivated by an organism's survival- are controlled by homeostatic mechanisms. - Amount of water in the body, the balance of dietary nutrients, and the blood sugar level. - Requires both neural and hormonal mechanisms. - Cells require certain concentrations of water, salt and glucose to function properly No regulatory behaviours - They are neither required to meet the basic survival needs of an animal nor controlled by homeostatic mechanisms. - These behaviors include everything from sexual intercourse to presenting to such curiosity driven- activates as conducting psychology experiments. - Sexual intercourse entail the hypothalamus but most of them don’t. - Such behaviours nettle a variety of forebrain structures especially the frontal lobes. - These behaviours are strongly influenced by external stimuli Regulatory function of the hypothalamic circuit - Maintains homeostatic by acting on both the endocrine system and the autonomic nervous system (ANS) to regulate our internal environments.

Hypothalamic involvement in hormone secretions - Function of the hypothalamus is to control the pituitary gland, which is attached to it by a stalk. - Lateral hypothalamus composed of both nucleic and nerve tracts running up and down the brain connects the lower brainstem to the forebrain. - Principal tract is the medial forebrain bundle (MFB). - MFB connects brainstem structures with various parts of the limbic system and forms the activating projections that run from the brainstem to the basal ganglia and frontal cortex. - Dopamine- Containing MFB fibers contribute to the control of many motivated behaviors, including eating and sex. - Each hypothalamic nucleus is anatomically distinct and has multiple functions in part because the cells in each nucleus contain a different mix of peptide neurotransmitters. ➔ When peptide neurotransmitters act we may experience a range of feelings like well- being (endorphins) or attachment (oxytocin and vasopressin). ➔ Neurons in the hypothalamus make peptides that are transported down their axons to terminals lying in the posterior pituitary. ➔ If these neurons become active, they send action potentials to the terminals to release the peptides stored there. ➔ Capillaries in the posterior pituitary rich vascular bed pick up these peptides. ➔ Peptides then enter the bloodstream which carries them to distant targets where they exert their effects. Hypothalamus and pituitary gland ● Hormones are synthesised here and sent to axon terminals in the posterior pituitary. ● Hormones released by axon terminals in the posterior pituitary are picked up by capillaries and carried into the bloodstream. ● Releasing hormones are synthesised here and secreted into capillaries that carry them to the anterior pituitary. ● Relapsing hormones then leave the capillaries and act on hormone- secreting anterior pituitary cells - Glandular tissue of the anterior pituitary synthesises various hormones. - Hypothalamus controls the release of these anterior pituitary hormones by producing Releasing Hormones peptides that act to increase or decrease hormone release. - A releasing hormone can either stimulate or inhibit the release of an anterior pituitary hormone. - Hormones that are released by the anterior pituitary in turn provide the brain a means for controlling what is taking place in many other parts of the body.

Three factors that control hypothalamic hormone regulated activity 1. Feedback loops - When thyroid hormone is low, the hypothalamus releases thyroid stimulating hormone-releasing hormone (TSH releasing hormone) which stimulates the anterior pituitary to release TSH. - TSH then acts on the thyroid gland to secrete more thyroid hormone. - Receptors in the hypothalamus detect the thyroid hormone level. - When the level rises the hypothalamus lessens its secretion of TSH releasing hormone. - Feedback mechanism; system in which a neural or hormonal loop regulates the initiation of neural activity or hormone release. 2. Neural control - hormonal activities of the hypothalamus regulation by other brain structures like the limbic system and frontal lobes. - Excitatory and inhibitory influences exerted by cognitive activity imply that the cortex can influence neurons in the periventricular region. - It is likely that projections from the frontal lobes to the hypothalamus perform this role. 3. Experiential responses - The brain's response to experiences; neurons in the hypothalamus undergo structural and biochemical changes just as cells in other brain regions do. - Hypothalamic neurons are like neurons elsewhere in the brain in that they can change by heavy demands on them. - Such changes in hypothalamic neurons can affect hormone output.

Hypothalamic involvement in generating behaviour - The hypothalamus is also the central in generating behaviour. - Two more important characteristics of behaviour generated by hypothalamic stimulation are related to: 1. oSurvival 2. oReward Organising function of the limbic circuit - Generates motivation and emotional behaviours. - The limbic system is formed from a primitive three-layered cortex known as the all cortex which lies adjacent to the 6-layered neocortex. - Hippocampal formation includes the hippocampus- a cortical structure important in species- specific behaviours, memory and spatial navigation and vulnerable to the effects of stress. - The Para hippocampal cortex.

Organisation of the limbic circuit - Role in emotion. - Limbic lobe and associated subcortical structures provide the neural basis of emotion. - Neural circuit tract known as PAPEZ CIRCUIT whereby emotion could reach consciousness, presumed at that time to reside in the cerebral cortex. - Hippocampus, amygdala and prefrontal cortex all connect to the hypothalamus. - Mammillary nucleus of the hypothalamus connects to the anterior thalamus which in turns connects with the cingulate cortex. - Cingulate cortex completes the circuit by connecting with the hippocampal formation, amygdala, and prefrontal cortex. - Most limbic structures perform important roles in various motivated behaviors as well, escpially in motivating species typical behavior such as feeding and sexual behavior. Amygdala - Consists of three principal subdivisions: 1. Corticomedial area. 2. Basolateral area 3. Central area - It receives inputs from all sensory systems. - More complex stimuli are necessary to excite amygdala neurons. - Many of these neurons are MULTIMODAL; they respond to more than one sensory modality. - Amygdala sends connections to the hypothalamus and the brainstem where it influences neural activity associated with emotions and species- typical behaviour. Executive function of the frontal lobe - Amygdala is connected to the functioning of the frontal lobe that constitutes all cortical tissues anterior to the central sulcus. - Motor cortex controls fine movements. - Premotor cortex participates in selecting appropriate movements.

Prefrontal anatomy and connections - PREFRONTAL CORTEX (PFC); Is anterior to the premotor cortex. - Key to controlling functions like planning movements. - Three primary areas 1. Dorsolateral regions 2. Orbitofrontal cortex 3. Ventromedial PFC - Co trolls the processes by which we select movements appropriate to the particular time and context. - Frontal lobes revive highly processed information from all sensory areas and many neurons in the prefrontal cortex, those in the amygdala are multimodal. - Prefrontal cortex receives input via connections from the amygdala, dorsomedial thalamus, sensory association cortex, posterior parietal cortex and dopaminergic cells of the ventral tegmental area. - Dopaminergic input is important for regulating how prefrontal neurons react to stimuli, including emotional ones. - Abnormalities to the dopaminergic projections may account for some disorders like schizophrenia. Areas in which the prefrontal cortex sends connections- its output; - Inferior prefrontal region projects axons to the amygdala and the hypothalamus in particular. - These PFC axons provide a route for influencing the ANS and ENS, which control changes in blood pressure, respiration and other internal processes - Dorsolateral prefrontal region sends its connections primarily to the sensory association cortex, posterior parietal cortex, cingulate cortex, basal ganglia and premotor cortex. Prefrontal cortex - Takes place in selecting behaviours appropriate to the particular time and place. - Disruption to these selection functions can be seen in people with injury to the dorsolateral frontal lobe. - They become overly dependent on environmental causes to determine their behaviour. - Adapting behaviour appropriate to the environment content is a PFC function. - The size of the frontal lobe is related to species sociability. - Social behaviour is rich in contextual information and humans are highly social animals. - People with damage to the orbital prefrontal cortex are common in traumatic brain injuries and have difficulty adapting their behaviours into social context. - The role of the frontal lobes in selecting behaviours is important for considering what causes behaviours. - The frontal lobe acts like a composer but instead of selecting notes they select our actions. They house our brain's executive functions.

Stimulating and expressing emotion - Three forms of emotional experience suggest the influence of different neural systems - The autonomic component must include the hypothalamus and associated structures as well as the enteric nervous system. - This perspective implies that the brain (cortex) produces a cognitive response to autonomic information. - James- Lange theory, named for its originators but all assume that the brain concocts a story to explain bodily reactions. - Two lines of evidence support this theory. 1. Same atomic responses can accompany different emotions. Particularly emotions are not tied to unique automatic changes. 2. Physiological changes are the starting point for emotions coming from people with reduced information about their own autonomic arousal. An example is the spinal cord. Spinal injury occurs in a decrease in perceived emotion and its severity depends on how much sensory input is lost. 3. People with the greatest loss of sensory input, which occurs with injuries at the uppermost end of the spinal cord, also have the greatest loss of emotional intensity. 4. SOMATIC MARKER HYPOTHESIS; Link between emotional and cognitive factors. - A sensory representation of the bear in the visual cortex is transmitted directly to the brain structures, like the amygdala that initiate emotional response - Domain somatic marker hypothesis : Proposes how emotions are normally linked to a person’s thought, decisions, and actions Ina typically environmental state, certain brain regions send messages to many other brain areas and to most of the reset of the body through hormones and the ANS. Amygdala and environmental behaviour - Influences emotion. - Kluver-bucy syndrome: Is the removal of the amygdala and anterior temporal cortex of monkeys. The principal syndrome includes the following 1. Tameness and loss of fear. 2. Indiscriminate dietary behaviour (eating many types of formerly rejected foods). 3. Greatly increased autoerotic homosexual and heterosexual activity with inappropriate object choice. 4. Tendency to attend to and react to every visual stimulus. 5. Tendency to examine all objects by mouth. 6. Visual agnosia, an inability to recognize objects of drawings of objects - Visual agnosia results from the damage to the ventral visual stream in the temporal lobe which are similar symptoms to amygdalate. ➔ To improve their sense of survival most organisms using fear as a stimulus

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minimise their contact with dangerous animals and maximise their contact with safe things. Olfactory information connects directly to the amygdala in the human brain. Olfactory causes predominate. Damage to the amygdala interferes with all these behaviours. ➔ Species survival requires a functioning amygdala. ➔ It influences autonomic and hormonal responses through its connections to the hypothalamus. ➔ It influences our conscious awareness of the positive and negative consequences of events and objects through its connections to the prefrontal cortex.

Prefrontal cortex and emotional behaviour - Frontal lobotomy destroys substantial brain tissue as the result of inserting a sharp instrument into the frontal lobes and moving it back and forth. - ...