Outline Brain Anatomy Structures and functions Disorders caused by lesions Comparative Anatomy Brain Function Cells in the brain How brain cells communicate Drugs on the Brain Mechanisms of action Drug addiction

Structural Anatomy Or Lateral Sulcus The human brain is folded and convoluted. Each ridge is called a gyrus, and each groove is called a sulcus (very deep sulci are often called fissures). The folding allows for increased cortical area; the cortex “unrolled” would be about 2.5 square feet. This allows for increasingly complex processing (more area = more cells = higher processing capability) Or Lateral Sulcus

Functional Anatomy Functional Areas of the Brain Executive Function Specific areas of the brain are important for specific functions – the brain is highly organized! Different areas of the brain have different functions. Functional Areas of the Brain

Language WERNICKES AREA: LANGUAGE COMPREHENSION BROCA’S AREA: LANGUAGE PRODUCTION For example, we might think of language comprehension and language production as being one phenomenon. In fact, the brain processes these components of language separately, and it is possible to lose on aspect without losing the other. When an area of the medial temporal lobe (Wernicke’s area) is damaged, a phenomenon called Wernicke’s aphasia occurs. People with receptive aphasia are unable to understand language in its written or spoken form, and even though they can speak with normal grammar, syntax, rate, and intonation, they cannot express themselves meaningfully using language. On the other hand, damage to Broca’s area might result in errors in speech production. Sufferers of this form of aphasia exhibit the common problem of agrammatism. For them, speech is difficult to initiate, non-fluent, labored, and halting. Writing is difficult, as well.

Wernicke’s Aphasia https://www.youtube.com/watch?v=dKTdMV6cOZw

Broca’s Aphasia http://auditoryneuroscience.com/brocas_aphasia

Two Interconnected Hemispheres Right and left hemisphere, connected by giant fiber bundle called the corpus callosum. The right hemisphere of the cortex excels at nonverbal and spatial tasks, whereas the left hemisphere is usually more dominant in verbal tasks such as speaking and writing. The extent of specialized brain function by an area remains under investigation. It is claimed that the difference between the two hemispheres is that the left hemisphere is "analytic" or "logical" while the right hemisphere is "holistic" or "intuitive." The right hemisphere controls (and receives sensory input from) the left side of the body and the left hemisphere controls (and receives sensory input from) the right side. Many simple tasks, especially comprehension of inputs, require functions specific to both hemispheres and thus require communication between hemispheres. The corpus callosum is a giant fiber bundle that allows the two hemispheres to “talk” to each other. As a last resort treatment for epilepsy the corpus callosum may be severed (this keeps the seizure activity from spreading between the hemispheres). Severing the corpus callosum results in “split brain syndrome”. People with split brain syndrome appear relatively normal and can pretty much function normally. However, some interesting symptoms do result from this intervention. When patients with a split brain are shown an image in their left visual field (the left half of what both eyes take in) they cannot vocally name what they have seen. This is because the speech-control center is in the left side of the brain in most people, and the image from the left visual field is sent only to the right side of the brain (those with the speech control center in the right side experience similar symptoms when an image is presented in the right visual field). Since communication between the two sides of the brain is inhibited, the patient cannot name what the right side of the brain is seeing. The person can, however, pick up and show recognition of an object (one within the left overall visual field) with their left hand, since that hand is controlled by the right side of the brain.

Split-Brain Phenomenon https://www.youtube.com/watch?v=aCv4K5aStdU

Internal Structures of the Brain THALAMUS: various nuclei serve as relay centers to the cortex from subcortical areas; all sensory systems have a thalamic relay (except olfaction) HYPOTHALAMUS: homeostasis; important in temperature, thirst, hunger, sexual behavior PITUITARY: hormone secretion (so that hypothalamus and periphery can communicate about homeostasis); connected to brain by infundibular stalk CORPUS CALLOSUM: fiber bundle connecting left and right hemispheres CEREBELLUM: balance and postural control, learning and memory MIDBRAIN: arousal, motor control, sleep/wake cycles PONS: “bridge”, connects midbrain to cerebellum MEDULLA: respiration, heartrate, blood pressure

Internal Structures of the Brain

VENTRICULAR SYSTEM Two lateral ventricles curve through each hemisphere, separated by the septum pellucidum: corpus callosum forms the roof, hippocampus forms the floor Lateral ventricals connected to third ventrical via intraventricular foramen (Foramen of Monroe) Third ventrical located in the midbrain, narrows to become the cerebral aqueduct Fourth ventrical lies between cerebellum (dorsal) and and pons/medulla (ventral), narrows to form central canal (continues into spinal cord) Fourth ventrical contains three openings (apetures) that allows CSF to flow freely into the subarachnoid space CSF is produced by choroid plexus, circulates through and around the CNS, eventually reaching the venus system

Comparative Anatomy: Structure = Function Brain structure tells us a lot about how smart an organism is, how it interacts with the world, etc.

RAT BRAIN Show rat brain: What animal do you think this comes from? What do you notice about this brain? Etc.

CAT BRAIN

PIG BRAIN

MONKEY BRAIN

Neurons: Cellular Communicators DENDRITES NUCLEUS CELL BODY MYELIN SHEATH AXON AXON TERMINALS

Neurons: Cellular Communicators Electrical Signal Action Potential Chemical Signal Neurotransmitter Release Receptor Binding

Neurons Form Networks

Action Potential

Cellular Communication: Sensory Acuity

Sensory Cortex

Sensory Units To Sensory Cortex RECEPTIVE FIELD: the spatial region where application of a stimulus causes a sensory neuron to respond receptive fields can overlap definition applies to higher order neurons, as well as to primary afferents SENSORY UNIT: a primary afferent and the receptors that define its receptive field

Receptive Fields 1. RECEPTIVE FIELD SIZE: the smaller the receptive field, the better the acuity 2. RECEPTOR DENSITY: the more receptors per receptive field, the better the acuity generally, receptors are concentrated in the centre of the receptive field Acuity the ability to localize a discriminative touch stimulus is called POINT LOCALIZATION, and it is dependent upon receptive field size, which varies widely throughout the body a simple way to measure somatosensory acuity is to determine the physical distance required for two stimuli to be perceived as separate = TWO POINT DISCRIMINATION the lips have the greatest acuity (two point discrimination threshold ~ 1 mm); the calf has the least (threshold ~ 48 mm)

Two-Point Discrimination Pick a partner Have them close their eyes Use paperclip (unfolded) to activate two sensory receptive fields Decrease distance between points until only once sensory receptive field is activated Arm Hand Back Record the distance between the points to get a rough estimate of regional sensitivity

Two-Point Discrimination Which area was most sensitive? Which are was least sensitive? What does this tell you about the sensory receptive field size of each area tested?

Drugs of Abuse How do drugs like nicotine and alcohol affect the brain? Why do these drugs produce a “high” while other drugs that act on the brain (such as asprin) don’t have this effect?

Drugs Hijack Brain Pathways (endogenous vs exogenous ligands) Remember that receptors are the proteins within synapses that receive signals from presynaptic neurons. Only certain molecules can bind to a receptor. Those molecules can be neurotransmitters already present in the brain, or they can be drugs that have entered the brain. When a molecule finds the receptor that it belongs to, it fits into the receptor like a key into a lock. And much like opening a lock, a molecule binding to a receptor will be able to open or close doors. The doors are ion channels on the post-synaptic neuron, which will allow the neuronal signal to continue traveling through the post-synaptic neuron to the next synapse.

Example: Dopamine Reward Pathway Dopamine release occurs in resposne to natural rewards

Cocaine Increases “Reward” Signal Cocaine heightens this natural rewarding feeling, increasing the levels of dopamine WAY above what occur naturally. Illustrate this by telling a story, such as the following: Cake is rewarding, right? We all like cake, we’ll eat cake even if we’re full. This is because our brain responds to sugar and fat by increasing dopamine signaling, which activates the reward system. Humans and other animals evolved to respond to high calorie food, because these foods increase our fat stores and give us energy (was more advantageous before these high-calorie foods were everywhere, but the point remains). However, you’ve never heard of someone robbing their own parents to get cake, right? Nobody takes it that far. But it’s not unusual for people addicted to cocaine to go to great lengths to get this drug, even breaking the law, even in the face of extreme consequences like loss of their family and job. This is because drugs like cocaine take that natural reward and AMPLIFY it. Much more rewarding than most natural rewards.

Mechanisms (Simplified) http://learn.genetics.utah.edu/content/addiction/drugs/mouse.html Drag mice and get a short overview of how each drug works on the brain (super simplified, but fine for this purpose)

What is tolerance? Tolerance occurs when you are abusing a substance/drug and over time your sensitivity to that substance decreases. Higher quantities of the substance/drug must be consumed in order to achieve the same effects as before. For example, a person has to drink more alcohol to reach a “buzz” than when he/she started drinking for the first time. Transition to discussing addiction process

What is physical dependence? Dependent upon a substance/drug to have normal function. Develop negative withdrawal symptoms when the substance/drug is no longer on board. Withdrawal symptoms are basically the opposite of the drug effects Withdrawal from stimulants: depression, lethargy Withdrawal from depressants: anxiety, sleeplessness

What is a standard drink?

What is Moderate Drinking? Women Men Moderate Drinking (“Low Risk”) Per Day 3 or less 4 or less Moderate Drinking (“Low Risk”) Per Week No more than 7 drinks No more than 14 drinks Heavy drinking would be considered consuming more than the daily amount or weekly amount listed in the table.

Alcohol Effects: Chronic Use Normal “Happy” Brain

Your brain wants to compensate Alcohol on the Brain

Your brain wants to compensate Alcohol Withdrawal

What is considered a binge? Binge drinking is consuming so much alcohol that your blood alcohol concentration (BAC) reaches 0.08g/dl or higher within 2 hours. For women: 4 drinks or more within 2 hours For men: 5 drinks or more within 2 hours

Withdrawal symptoms increase in severity after multiple relapses

Cycle of Addiction

Alcoholism can cause loss of brain matter over time

Impaired Brain Activity in Alcohol Dependence

Questions?