Chapter 4

1. Chapter 4 The Biology of Behaviour Chapter 4 - The Biology of Behaviour

2. Sections • The Brain and its Components • Studying the Brain • Control of Behaviour • Control of Internal Functions and automatic behaviour • Drugs and behaviour Chapter 4 - The Biology of Behaviour

3. The Brain and its Components • The Structure of the Nervous System • Cells of the Nervous System • The Action Potential • Synapses • A Simple Neural Circuit • Neuromodulators Chapter 4 - The Biology of Behaviour

4. Structure of the Nervous System Steve, show BIO15 overhead here depicted the brain with the above structures indicated Chapter 4 - The Biology of Behaviour

5. Protectingthe CNS For protection purpose, both the brain and the spinal cord are incased in bone (the skull and spine respectively) In addition, both the brain and spinal cord are separated from their bony armor by a 3-layered set of membranes called the meninges. Between the two layers of meninges is a clear liquid called the cerebral spinal fluid. This fluid in combination with the meninges provides a “waterbed” of sorts that protects the sensitive CNS from becoming damaged by the bone that surrounds them Chapter 4 - The Biology of Behaviour

6. The Cerebral Cortex Our most complex psychological processes occur within the thin layer of grey matter on the outside of our brain called the cerebral cortex The cortex is connected to the other parts of the brain through a set of nerve fibers called white matter (see figure 4.3 in the book for a look at this distinction) In order to maximize the size of the cortex, the human brain has become wrinkled, containing fissures and gyri Chapter 4 - The Biology of Behaviour

7. Structure of the Nervous System Steve, show BIO2 overhead here depicted the brain with the above structures indicated Chapter 4 - The Biology of Behaviour

8. Cells of the Nervous System The basic unit of the human nervous system is the cell. The nerve cell is made up of four parts, (1) the dendrites, (2) the soma, (3) the axon, and (4) the axon terminals. > BIO7 overhead … note myelin Neurons transmit information through electrical currents termed action potentials that flow from the soma, through the axon, to the axon terminals … where it is then passed to the dendrites of other neurons > wave demo & overhead BIO8 Chapter 4 - The Biology of Behaviour

9. Transmission of Information Between Cells Information is passed from one cell to another via a process termed synaptic transmission This process involves the release of neurotransmitter molecules from one neuron which then “fit into” receptor sites on the dendrites on other neurons - BIO9 overhead. Some neurotransmitters send excitatory signals, some inhibitory. These signals are summed by the soma of the receiving neuron which “decides” whether to send an action potential - BIO10 After the signal is sent, the neurotransmitters return to the sending neuron in a process termed re-uptake. Chapter 4 - The Biology of Behaviour

10. A Simple Neural Circuit To illustrate this system in action, consider the following two situations: 1. Touching a hot iron … sensory neurons detect the heat and send an excitatory message to inter-neurons in the spinal cord or brain. These inter-neurons then send excitatory signals to the motor neurons to retract the hand immediately 2. Carrying a hot casserole dish … again, the heat may make you want to drop the dish via the same process described above, BUT this message is temporarily countered by the brain by it sending inhibitory signals either to the inter-neurons or to the motor neurons Chapter 4 - The Biology of Behaviour

11. Neuromodulators As described, neurons send messages to other neurons via chemicals calledneurotransmittersorneuromodulators. These chemicals can effect many sites in the brain simultaneously leading to many different behavioural effects Humans have also used synthetic versions of these chemicals sometimes for recreational (or abusive) purposes and sometimes for therapeutic purposes. > e.g., Marijuana question Chapter 4 - The Biology of Behaviour

12. Study of the Brain Much of our understanding of nerve cells has come from studies conducted on animals Animal research has also lead to the discovery of a number of drugs that have helped patients suffering from such diseases as Parkinson’s syndrome, schizophrenia, depression and others The use of animals is considered justified in two ways: 1) in some cases in leads to obviously beneficial results for humans as in the case of drug studies 2) in other cases, it advances our knowledge of the human system which is considered worthwhile in and of itself Chapter 4 - The Biology of Behaviour

13. RM - Lesion Studies One of the oldest research methods used by physiological psychologists involves examining the behavioural effects of damage to certain parts of the brain. Typically, this involves having the researcher creating alesion through a surgical procedure in order to wipe out the specific part of the brain they are interested in - see BIO1 overhead for a depiction of thestereotopic apparatusused to do this The “destruction” of brain tissue is usually done by touching a small wire to the brain site of interest, then passing an electrical current through the wire in order to heat and destroy the area A similar procedure is also sometimes used on humans to alleviate symptoms of some diseases Chapter 4 - The Biology of Behaviour

14. RM - Measurement & Stimulation Electrodes inserted via surgical procedures can also be used to measure the activity in nerve cells in response tostimulation The electrode is then connected to a recording device and measuresof electrical activity can be taken while the animal performs various tasks Electrodes can also be used to stimulate brain areas without destroying them … and effects of stimulation can be studied > famous rat self-stimulation experiment Sometimes the stimulation and measurement are combined to examine things like learning … long-term potentiation example Chapter 4 - The Biology of Behaviour

15. Enter the Reaper Irrespective of the study, after it is done the researcher has to verify that the electrode was in the location (s)he thought it was in. The typical procedure for doing this involves > sacrificing the animal via drug overdose > removal of brain > slicing up of brain > dying of the brain slices > examination of the sliced and dyed brain to verify location Sometimes, in order to stain the brain appropriately a more complicated procedure must be used callprofusion… Steve will explain I’ll be leaving now, thanks! Chapter 4 - The Biology of Behaviour

16. Human Subjects Clearly, many of the procedures we perform on animals would not be considered ethical if performed on humans However, there are now means of doing things that parallel the animal work … thanks largely to brain scanning technology CT (computerized tomography)scans send a narrow beam of X-rays through the head and the computer calculates the amount of radiation that passes through, then is able to generate a “slice” of the brain, showing brain density at specific regions - BIO13 MRI (magnetic resonance imaging)do the same thing as CTs, but with more detail (uses magnetic fields and radio waves instead of X) PET (positron emission tomography)scans measure processing rather than structure by examining blood flow Chapter 4 - The Biology of Behaviour

17. Methods that Parallel Animal Work Given these scanners, we can now describe at least two methods that parallel those done with animals First, due either to natural (e.g. stroke) or unnatural (e.g., accident) situations, human brains become damaged -- or lesioned. Scanners can now be used to localize the damage, and behavioural methods can be used to assess the relation between certain brain areas and certain behaviours Second, we can also measure processing in the brain (via a PET) while the subject engages in some activity … much like using electrodes to measure processing in the rat brain Chapter 4 - The Biology of Behaviour

18. So, what have we learned about the brain from all this? The cerebral cortex vs. lower level brain structures The cerebral cortex is the place where high level perception of the world occurs, and is also the place where controlled motor activities originate. In this sense, it is the place where all our controlled interactions with the external world occur. This contrasts with a number of more basic brain regions which are more devoted to monitoring and controlling internal behaviours and automatic responses to external stimuli. Each will now be discussed in turn Chapter 4 - The Biology of Behaviour

19. The Cerebral Cortex Primary Motor and Sensory Cortex: > There most definitely are certain parts of the brain that are responsible for very specific tasks, especially when it comes to sensation and motor responses - BIO18, and FIG 4.23 > These areas are organized in a contralateral manner, such that the left side of the brain represents the right side of the body, and vice-versa > The amount of brain dedicated to various regions is not determined by the size of the region but, instead, by the sensitivity of it - sensory homunculus Chapter 4 - The Biology of Behaviour

20. The Cerebral Cortex Association Cortex The remainder of the cerebral cortex is termed “association cortex” and is thought to be where sensations are drawn together to support higher level cognitive functions such as perception, learning, and memory - Penfield’s surgery Perception, then, is not the same as sensation but, instead, is the interpretation of that sensation as performed by the association cortex - CAT IN THE HAT example The association cortex is often discussed in terms of lobes of the brain; frontal, occipital, parietal & temporal - FIG 4.24 Distinction between somatosensory vs motor association cortex Chapter 4 - The Biology of Behaviour

21. Sensation is not Perception Chapter 4 - The Biology of Behaviour

22. The Cerebral Cortex Lateralization of Function The two hemispheres of the brain do not perform identical functions … rather, each hemisphere seems to specialize in certain things - BIO23 We are not aware that the hemispheres perceive the world differently because they completely communicate with one another via a brain structure called the corpus collosum In certain extreme cases of epilepsy, the corpus collosum of a patient is severed, in order to prevent the siezures. This leads to an interesting splitting of experience from awareness - BIO24 … more to come in Chapter 9 Lateralization is less clean than implied Chapter 4 - The Biology of Behaviour

23. The Occipital & Temporal Lobes The occipital (and lower part of the temporal) lobes are devoted to vision. Primary visual cortex is directly related to sight, and damage to it produces a hole in a persons visual field … a scitoma Association cortex in this area performs the function of providing an interface between visual input and memory … allowing one to categorize visual images. Damage can lead to agnosia, the inability to name common objects A Pencil? Chapter 4 - The Biology of Behaviour

24. The Temporal Lobe Most of the temporal lobe is devoted to audition Primary auditory cortex is mostly hidden from view, lying on the inside to the upper temporal lobe. Damage to this leads to hearing problems Auditory association cortex is located on the lateral surface of the upper temporal lobe > Damage to left leads to severe language deficits … patients losing the ability to comprehend or produce meaningful speech > Damage to the right affects the patients ability to properly perceive non-speech sounds, like the rhythm in music Chapter 4 - The Biology of Behaviour

25. The Parietal Lobe Primary sensory function involvesperception of the body The association cortex here seems to be involved incomplex spatial functions, that differ across the hemispheres The left parietal appears to keep track of the spatial location of our body parts - proprioception > Damage often associated with poor motor movements The right parietal appears to keep track of the spatial location of things in our external world > Damage can lead to problems of neglect and spatial integration of parts Chapter 4 - The Biology of Behaviour

26. The Frontal Lobes Thought to be responsible for many very high level cognitive functions such as planning, strategy shifting, self-awareness, and the initiation of motor activity. Damage to the motor area of frontal cortex causes paralysis of the associated motor functions in the opposite side of the body Damage to the pre-frontal cortex ( e.g. frontal labotomies) causes very complex and interesting effects including: 1. The slowing of thoughts and loss of spontaneity 2. Perseveration errors - Card sorting example 3. Loss of self-awareness and flat affect, especially empathy 4. Deficiencies in foresight and planning 5. Tendency to confabulate Chapter 4 - The Biology of Behaviour

27. Wisconsin Card Sorting Task Sort by number Sort by shape Sort by colour Chapter 4 - The Biology of Behaviour

28. Sub-cortical Brain Regions The brain stem is involved in many of our most basic behaviours including the control of heart rate, blood pressure, and respiration (medulla), sleep (pons), fighting and sexual behaviour (midbrain) Thecerebellum, in co-ordination with the frontal lobes, carries out the detailed computations necessary for precise motor movements … in addition it also controls adjustments for posture, and corrects for things like head movement when controlling eyes In addition, there are also a number of regions within the cerebral hemispheres that also play a role including thethalamus, the hypothalamus, and thelimbic system Chapter 4 - The Biology of Behaviour

29. The Thalamus and Hypothalamus The thalamus, located in the very center of the brain, performs two basic functions; (1) the reception and integration of perceptual information, and (2) the passing on of this information to the relevant cortical regions … attention?? The hypothalamus is located below the thalamus and is very small. It monitors a number of characteristics of the blood that flows thru the brain (e.g., temperature, composition) and controls the pituitary gland, an endocrine gland attached to the base of the skull Endocrine glands release hormones which act like neurotransmitters except over longer distances … they stimulate receptor sites causing physiological reactions The pituitary is the master endocrine, as it can command target receptors on other endocrine glands Chapter 4 - The Biology of Behaviour

30. The Limbic System Includes two structures, the amygdala, and the hippocampus. The amygdala appears to control emotional reactions, especially negative ones. In addition it provides energy for fighting and fleeing > damage to the amygdala causes a loss of “stress” and “anger” reactions … which is actually bad news for survival The hippocampus plays an important role in memory. It is especially critical for learning new information … many of those most striking cases of amnesia are caused by damage to the hypocampus Chapter 4 - The Biology of Behaviour

31. Drugs and Behaviour This section I leave to you … I will not discuss it beyond that which we have done already … you are responsible for it though, so read up! Chapter 4 - The Biology of Behaviour