HMB200H1 Final: L1 Does the Brain Change Itself?

18 Pages
Unlock Document

Human Biology
Franco Taverna

Lecture 1 Does the Brain Change Itself? Kolb & Whishaw 5E: § 1-1 to 1-3, 2-1, 2-3, 2-6, 4-4, 11-1 to 11-2, 11-4 (spinal reflexes), 11-5 Neuroscience Online: §3 Ch. 1.1-1.7, 2.1, 3.5, Fig. 3.1-3.3; §4 Ch. 12.1-12.2, 12.6-12.7, Fig. 12.7 Tuesday, January 10 Lecture Outline: I. Why did the chicken cross the road? II. Course logistics and goals III. How did the chicken cross the road? a. Explaining behaviour in terms of brain activity and homunculus IV. The brain as an adaptive organ I. Why did the chicken cross the road? The Brain The Brain – is wider than the Sky – For – put them side by side – The one the other will contain With east – and you – beside The Brain is deeper than the sea – For – hold them – blue to blue – The one the other will absorb – As sponges – buckets – do – Emily Dickinson, ca 1860 • Why questions aren’t the easiest for scientist, but especially for neuroscientists • Based on neural activity? Motivation? This seems like a complex endeavour because the brain is complex in and of itself • Neuroscientist might answer this based on the activity of the brain • Difficult to understand even simple behaviours based on such complexity • Approach the question backwards, breaking it down and reducing it into manageable steps • Can we explain the very last step? What was behind, in terms of activity, that very last step? o Of course, we can measure it, record it, and even image it What is Neuroscience? “The role of neuroscience is to explain behaviour in terms of the activities • Behaviour and influencing or adapting such of the brain. How does the brain marshal its millions of individual nerve • Today, we will try to answer the question “why did the cells to produce behaviour, and how are these cells influenced by the chicken cross the road?” environment…? The last frontier of the biological sciences – their ultimate • Then we’ll switch the question to how – easier to tackle challenge – is to understand the biological basis of consciousness and the at reasonable levels of understanding mental processes by which we perceive, act, learn, and remember.” • Introduce the idea of adaptation with the brain as an adaptable organ - Professor Eric Kandel, Director of Columbia University’s Centre for Neurobiology and Behaviour, Nobel Prize Winner for Medicine 2000 The Brain’ Cont’d… II. Course logistics and goals Introduction to Teaching Staff Note: may switch up TAs over the term • Franco Taverna, Associate Professor, Human Biology • Wetmore Hall (WE) 132A • [email protected] • (416) 946-5048 • TAs: Geith Maal-Bared, James Samsom, Amy Oh, Samantha Yammine, Nicole Teschl, Maryna Pilkiw o Support learning, unable to answer questions about course administration and grades Research Where am I? Hippocampal neuron activity correlated to spatial location. • O’Keefe’s place cells in the hippocampal region based on spatial navigation • Activity of cells in the hippocampus as an organism navigates their environment HMB200H Introduction to Neuroscience An introductory course that explores the development, physiology and • Lectures will be for discussing concepts, rather than the details in the textbook continually changing function of the nervous system as it relates to certain types • More about thinking, analyzing, and problem of human behaviour. Emphasis is on plasticity in systems that underlie adaptive solving, rather than memorizing behaviours, maladaptive syndromes, and disorders. Critical analysis of scientific • Pre-lecture quizzes solely based on assigned evidence is used to enrich learning. textbook readings • Tutorials will include writing development as well, • Lectures: discuss key concepts weekly, evaluated on midterm and final with participation evaluation and content quizzes exam • Textbook: more comprehensive introduction to neuroscience, evaluated in pre-lecture quizzes, lesser extent on midterm and final exam • Tutorials: active learning with activities and skill development, evaluated in online quiz available during tutorial • Direct all questions about course administration to instructor and/or Human Biology Office at [email protected] 2 • Four sections of this introductory course • A principle of neuroscience is to create reality of the world in order to act on it, but it’s really a virtual reality • Plasticity and change is the theme of the course Required Readings For three decades, Canadians have trusted David Suzuki and The Nature of Things on issues of the environment, wildlife, technology, and medicine. The Nature of Things and David Suzuki • Brian Kolb, Ian Q. Whishaw, Campbell Teskey An Introduction to Brain and have paved the way for a greater understanding of the increasingly complex world in which we th live. The Nature of Things Canadian Broadcasting Corporation (CBC) documentary is based on Behaviour, 5 edition the best-selling book by Toronto psychiatrist and researcher Dr. Norman Doidge which presents • “Neuroplasticity changes everything” a strong case for reconsidering how we view the human mind. You may watch Dr. Michael Merzenich, Chief Scientific Officer at Posit Science, and the brain behind our Brain program in Part 2 (5:26). • • Can inspire topics for debate essay assignment Evaluation Assignment and Description Weight Date Pre-Lecture Quizzes See dates on syllabus. Online quizzes that are based on readings for a given lecture to help you prepare and better understand and Top 6 of 8 will count. the lecture material – due before the lecture (Tuesday 9am) Tutorial Quizzes + Assignments See dates on syllabus. Short quizzes or Assignments given at end of tutorial to incentivize participation and deeper learning of coTop 6 of 8 will count. content. Debate Essay (multiple components) th 1. Debate Questions and reflection* 2%* Tues. Feb. 7 2. Annotated Bibliography* 2%* Tues. Mar. 7th 3. Debate Essay Tues. Apr. 4th A short essay summarizing and critically evaluating a piece of evidence for two sides of a debate question, reflective writing assignment based on your entire placement Midterm Exam Tues. Feb. 14 10am- Multiple choice and some written answer questions, content and skills examined 20% 12pm Final Exam 45% Final exam period Written answer questions, non-cumulative content, but cumulative skills examined Quizzes 1. Pre-lecture quizzes completed online using Blackboard o Due 9am Tuesdays (see syllabus) o Based on readings for the week o To incentivize preparation for lecture 2. Tutorial quizzes completed online using Blackboard o Due by the end of tutorials o Based on material in tutorial o To incentivize attendance and participation in tutorial 3 Student Expectations How to Excel in HMB200H • Attendance, organization, deadlines, getting help 1. Spaced learning rather than cramming o Attending and participating is well worth it • Meet the instructor during drop-in hours: o Monday 10:30am-12pm, Wednesday 120:30am- o Plasticity-based reasons 12pm, Friday 2pm-3pm 2. Test yourself, rather than passively reading 3. Sleep well, eat well, exercise well • Phone meetings also welcome: (416) 946-5048 4. Build learning habits and organizational habits • Appointment by email What happens in the brain when breaks reinforce memories, especially with at least 3 hours of REM sleep? III. How did the chicken cross the road? Principle 1 of Neuroscience: The nervous system’s function is to produce movement within a perceptual world created by the brain Let’s analyze the last step of the chicken. • The first principle of neuroscience is similar to what Dan Wolpert said – the nervous system’s function is to produce movement, within a perceptual world created by the brain • Let’s take a historical perspective to examine how we determined the structure and function of nervous system, albeit incorrectly Historical Perspectives of Neuroscience: Rene Descartes • Inspired by the St. Germain mechanical statues in the 1600s (automata) • These automata would respond in certain ways • Reflexive behaviours whenever someone stepped on a lever for it – pulleys, levers, etc. • Descartes theorized that humans and animals behaved in the same way • Descartes believed the body was the same – with • Stimuli “vibrate” spirits in nerves (hollow tubes) to brain, through ventricles, and back down nerves to muscles hydraulics and tubes (nerves) with fluids/spirits running through them, resulting in the brain causing Descartes proposed dualism: muscle movement • Dangerous issue (due to religion) for human will, • Animal soul/sprits through ventricles causes simple behaviours/reflexes higher-order thinking, and the rational soul o Materialism = fixed • Believed rational soul was based on the pineal gland – • Rational soul (pineal gland) can modify those movements/behaviours where we get our ability to reason, think, change, and o Spiritualism = amenable learn, to act in the world with consciousness • Dualism = mechanical + spiritual dominated neuroscience for a long time Epigenetics: study of differences in gene expression related to environment and experience 4 a. Explaining behaviour in terms of brain activity and homunculus Modern View of Materialism of Movement Muscle activation occurs by neurotransmitter Acetylcholine (ACh). • Chemical transmitter that axon terminal releases at muscle end plate • Attaches to transmitter-sensitive channels • Channels open, slowing Na and K ions across the muscle membrane to depolarize the muscle to threshold • Muscles then generate action potentials to contract • Materialistic view is our modern perspective • Last step across the road involves contractions of muscles in the leg • NMJ was first studied structure in the nervous system – synapse was then described • Axon terminates onto a muscle motor end plate and across the muscle, there are receptors that bind NTs resulting in the opening of cation channels resulting in action potentials and contraction of muscles • A split second before the last step, the signal from those neurons to the muscle originated from the spinal cord Materialism of Movement • Spinal motor neurons activate muscles • Spinal motor neurons are in turn activated by neurons whose axons descend from the brain down the anterior spinal tracts • Cell bodies of motor neurons are found in the ventral horn of the spinal cord Bottom-Up; Muscles to Brain, Top-Down: Cortex to Muscles Corticospinal tracts (pyramidal tracts): main efferent pathways from the motor cortex to the brainstem to the spinal cord • Axons from these tracts originate mainly in motor cortex layer V pyramidal cells and from the premotor and sensory cortices • Axons descend into the brainstem, sending collaterals to numerous brainstem nuclei, and eventually emerge on the brainstem’s ventral surface, where they form a large bump on each side • Some axons descending from left hemisphere cross over to the right side of the brainstem and vice versa, while others stay on their original side o This division produces two corticospinal tracts, one crossed, and the other uncrossed, entering each side of the spinal cord o Lateral corticospinal tract: fibres that cross to the opposite side of the brainstem descend the spinal cord in a lateral position o Anterior corticospinal tract: fibres that remain on their original side continue form the brainstem down the spinal cord in an anterior position • Motor cortex: cortical motor neurons connect to brainstem or spinal neurons • Brainstem: executes species-specific behaviours (see Exp. 11-1) • Spinal cord: executes simple reflex motor actions • Some axons from the spinal cord synapsed from neurons in the motor cortex, while others begin in the brainstem or midbrain • All of them eventually have connections to the motor cortex 5 Spinal Cord: Executing Movement • In humans and other animals with a severed spinal cord, spinal • Spinal cord itself, due to its collection of motor neurons, can activate some of these behaviours reflexes still function even though the spinal cord is cut off • Reflexes occur without top-down input (upper levels influence how from communication with the brain information is processed in lower regions of the hierarchy) o Paralyzed limbs may display spontaneous movements • With postural support in severed spinal cord patients, reflexes can or spasms execute motor programs for walking simulation o Brain can no longer guide the timing of these automatic movements Brain Stem • Producing complex patterns of adaptive behaviour is an important brainstem function • Brainstem organizes many adaptive movements o Maintaining posture, standing upright, coordinating movements of limbs, swimming and walking, grooming fur, and making nests • Cerebral palsy: caused by brainstem trauma o Voluntary movements become difficult to make, whereas conscious behaviour controlled by the cortex may remain intact • Brainstem + spinal cord can also produce more species-specific behaviour Principle 4 of Neuroscience: The CNS Functions on Multiple Levels • Simple animals, such as worms, have a spinal cord while • At least 4 or 5 levels acting just on the last step – spinal cord, brain stem, rubrospinal tract, premotor cortex, motor cortex, etc. more complex animals, such as fish, have a brain stem as well, and yet more complex animals have evolved a • Lower levels are important for timing/speed, adaptivity of forebrain automatic behaviours (reflexes) – confer some advantage • Each new addition to the CNS has added a new level of behavioural complexity without discarding previous levels of control • Why keep these lower levels? The Outside World is Represented Within the Inside World • Penfield, neurosurgeon that worked on the cortex, discovered a lot about the cortex • Used electrical stimulation of certain parts of the brain and mapped the whole thing out • Confirmed the role of the primary motor cortex (M1) in producing movement in humans • We can study neuroscience by studying simple neural loops (spinal reflexes) or slightly more complex versions of them • This is why we use model organisms because the concepts are very similar Wilder Penfield Mapped the Brain • Penfield used stickers on the brain where he was stimulating a patient 6 Organization of the Motor Cortex: The Simple View • Topographic organization o Neural spatial representation of the body parts activated by the brain region • Proportional representation o Body parts with most dexterity have largest neural representation in motor cortex • Homunculus (little person) o Proportional representation of human body in sensory and motor cortex o Any topographical representation of the body by a neural area • There seems to be a topographical map on the motor cortex that corresponds to a part of the body • It’s less specific and complex than that though – there isn’t a 1:1 correspondence between a brain part and individual muscles • Rather, entire body parts • If you move the arm or elbow, there are many muscles involved, or even gripping something – this more closely describes what neurons in the brain are doing • In the spinal cord, there is a 1:1 neuron to muscle correspondence • There is a proportional representation though… Homuncular Man • Distortions illustrate the fact that extensive areas of the motor cortex allow precise regulation of hands, fingers, lips, and tongue • Areas of the body over which we have much less motor control have much smaller representation in the motor cortex • Muscles in the body that are the most dextrous have the largest real estate in the brain – this is pre-wired, and selected for such that we’re born this way • There is lots of flexibility in this The chicken last step occurred because the motor cortex was activated. Now we can ask the question why or how the chicken took the first step. Motor cortex activated the first step. What activated the motor cortex? Functional Organization of the Nervous System (a) Anatomical Organization • Brain and spinal cord make up the central nervous system • Nerve fibres radiating out beyond the brain and spinal cord, as well as neurons outside the brain and spinal cord, form the peripheral nervous system o Carries sensory information into the CNS and carry motor instructions from the CNS to the body’s muscles and tissues (b) Functional Organization • Neurons in the somatic division of the PNS connect through cranial and spinal nerves to receptors on the body’s surface and muscles o Somatic neurons gather sensory information for the CNs and convey information from the CNS to move muscles • Autonomic division of the PNS enables the CNS to govern the workings of the body’s internal organs • Enteric nervous system controls digestion and stomach contraction Form a functional standpoint, the major PNS division step up to constitute, along with the CNS, an interacting four-part system: 1. Central nervous system (CNS): brain and spinal cord which mediate behaviour 2. Somatic nervous system (SNS): all spinal and cranial nerves carrying sensory information to CNS from muscles, joints and skin, and transmits outgoing motor instructions that produce movement 3. Autonomic nervous system (ANS): balances body’s internal organs by producing rest-and digest response through parasympathetic nerves or fight-or-flight response through sympathetic nerves 4. Enteric nervous system (ENS): mesh of neurons embedded in lining of gut, mostly operating autonomously The directional flow of neural information is important. • Afferent information is sensory, coming into the CNS or one of its parts • Efferent information is leaving the CNS or one of its parts 7 Motor Cortex Triggers Movement Categories, Not Individual Muscles • Michael Graziano, (2006) recently concluded motor cortex represents a repertoire of fundamental movement categories • The primary motor cortex is activated by the premotor cortex The motor cortex takes part in planning movement, executing movement, and which is activated by the prefrontal cortex adjusting the force and duration of a movement. • When activated, the motor cortex triggers a specific movement • Neurons begin to fire even before a movement is made, suggesting that types involving collections of muscles and body parts = they take part in planning the movement as well as initiating it fundamental movement categories • What activates the prefrontal cortex? • Neurons continue to fire throughout the movement, confirming that they play a role in producing the movement Given a sensory stimulus (context), we can answer the question of wh• Neurons fire at higher rates when load changes suggesting that they play the chicken took the first step and hence what activated the frontal a role in adjustment of the movement’s force cortex. The motor cortex also plays a role in specifying the end point of a movement. • On-off neuronal responses are simple way of coding desired final position Principle 6 of Neuroscience: Brain Systems Are Organized of a movement Hierarchically and in Parallel • The same neurons in motor cortex are responsible for configuring various • Brain systems are organized hierarchically and in parallel movements that achieve the same end point produced when those same neurons are electrically stimulated • CNS comprises multiple levels of function • Levels must be extensively interconnected to integrate their Motor neurons can also be active even when no overt movement occurs. processing and produce unified perceptions or movements • During planning a movement, withholding movement on instruction, and mental imagery What Activates the Frontal Cortex? • Frontal lobe (executive function) o Motor cortex • Parietal lobe (sensory integration) o Projects to frontal lobe • Temporal lobe (auditory, gustatory, olfactory, memory) • Occipital (visual) • We see the hierarchical nature, but the parallel nature also comes into play in projecting to and controlling the motor cortex • All other parts of the brain project to the frontal cortex o Main input comes from the parietal lobe – association region o Parietal lobe gets input from other regions in the brain and projects forward (temporal and occipital lobes) o Most of the real estate of the cortex is dedicated to sensory processing and memory (temporal lobes) 8 Overview of Brain Function and Structure The brain’s primary function is to produce behaviour, or movement. • Brain must absorb information about the world o Without stimuli, the brain can’t orient the body and direct it to produce an appropriate response • Nervous system’s organs designed to admit information from world and convert information into biological activity that produces perception, subjective experiences of reality o Brain produces what we believe is reality so that we can move, essential to carrying out any complex task o Mental construct of reality is based not only on sensory information we receive but also on cognitive processes we might use to interact with that incoming information o Differences in subjective experiences across species is due merely to two differently evolved systems for processing sensory stimuli, allowing different animals to exploit different features in their environments • Evolution fosters adaptability, equipping each species with a view of the world that helps it survive Case Study 1: The Perceptual World Do we see with our eyes? • Visual areas occupy about 1/3 of the cortex • In humans, the visual system is important – how does it work and what is its purpose? • The brain is really what sees here, rather than the sensory organs They Eye and Retina is like a Camera Photons land on the retina, and are transduced into the impulses of the nervous system – virtual reality is created right off the bat in the photoreceptors of the retina. Complex Projections from Retina to Thalamus and Visual Cortex • We also see immediate divergent pathways and parallel pathways • From the optic nerve  pupillary reflexes and neck/head orientation, through to the midbrain areas (thalamus) and eventually back to the occipital lobe that houses the first cortical area dedicated to vision 9 Visual Cortex as a Feature Detector • This is about 5 synapses down the path • Discovered what neurons in the visual cortex are doing when cats are seeing certain things • Neurons in the visual cortex don’t respond to entire images, nor to individual dots or pixels (like a camera) • Rather, these neurons respond to diagonal lines in certain
More Less

Related notes for HMB200H1

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.