1 Psychology 304: Brain and Behaviour Lecture 32

2 Exam: December 11, 8:30-11:00 AM, Osborne A The exam is worth 25% of your final grade. The exam will be scored out of 75 points. The exam will cover Chapters 5, 7, 8 (p ), 9 and 10 (p , ) of the textbook and all material discussed in class since the midterm exam. The exam will include 40 multiple choice questions (1 point each), 5 definitions (2 points each), and short answer questions (2-8 points each, totaling 25 points).

3 Please arrive on time; students who arrive after a classmate has completed the exam and left the exam room will not be permitted to write the exam. Bring a pencil, eraser, pen, and your student ID to the exam. Electronic devices are not permitted at your desk. Due to concerns regarding theft, do not bring valuables to the exam room. Hats (e.g., baseball caps) should not be worn during the exam.

4 Reminder I will hold additional office hours in preparation for the December exam: Friday, December 3: 3:30-4:30 Thursday, December 9: 10:00-12:00, 1:00-3:00 Friday, December 10: 10:00-1:00

5 1. What is the structure of the eye and where are the receptors for light? (continued) 2. How is information about light relayed to the brain? The Visual System 3. What are the major areas of the brain that are associated with the perception of light?

6 By the end of today’s class, you should be able to: 1. distinguish between cones and rods. 2. explain how an action potential is generated in the retinal cells of the visual system. 3. review the pathway by which visual information is transmitted from receptors to the brain. 4. identify the locations and functions of the primary cortex, secondary cortex, and association areas for the visual system.

7 From last class ….

8 Convergence of Cones and Rods on Retinal Ganglion Cells

9 What is the structure of the eye and where are the receptors for light? (continued) The fovea is specialized for high-acuity vision. Visual acuity at the fovea is enhanced by: 1. the presence of cones. 2. the “thinning” of the bipolar and ganglion cell layers in this region.

10 The Fovea Cone vs. Rod Density at the Fovea

11 Retinal Cells at the Fovea

12 When light reaches a receptor, photopigments (e.g., rhodopsin) are activated that hyperpolarize the receptor cell. Reduced neurotransmission by the receptor cell results in depolarization of the adjacent bipolar cell (for “on-center” cells only).

13 In turn, depolarization of the bipolar cell results in depolarization of the adjacent ganglion cell. When the ganglion cell is stimulated, an action potential is triggered that passes down the cell’s axon, along the optic nerve—cranial nerve II.

14 Generation of an Action Potential in the Retina

15 How is information about light relayed to the brain? Visual information is relayed to the brain via many pathways. The largest and most studied visual pathway is the retina-geniculate-striate pathway. Within this pathway is the optic chiasm: at this point, axons from the nasal halves of the retinas “cross over” and ascend to the dorsal lateral geniculate nucleus (LGN) of the thalamus. Thus, each hemisphere receives information from the contralateral visual field.

16 Retina-Geniculate-Striate Pathway

17 The LGN contains six layers of neurons. The inner two layers are called magnocellular layers, and the outer four layers are called parvocellular layers. The parvocellular neurons are most responsive to color, fine pattern details, and stationary objects and receive the bulk of their input from cones. The magnocellular neurons are most responsive to movement and receive the bulk of their input from rods.

18 Layers of the LGN Magnocellular

19 What are the major areas of the brain that are associated with the perception of light? The thalamic neurons that receive visual information subsequently project the information to the primary visual cortex.

20 Primary Visual Cortex

21 Primary Visual Cortex

22 The primary visual cortex is organized into functional vertical columns (i.e., ocular dominance slabs, orientation columns). The retina-geniculate-striate pathway is characterized by retinotopic organization.

23 Ocular Dominance Slabs and Orientation Columns

24 Information received by the primary visual cortex is segregated into distinct pathways that project to areas of the secondary visual cortex and, then, the association visual cortex. Two main pathways from the primary visual cortex have been identified: The dorsal stream and the ventral stream. The dorsal stream is associated with location and movement; the ventral stream is associated with identification.

25 The Dorsal and Ventral Streams

26 VI: Location, orientation, colour V2: Form, relays information V3: Form V4: Colour, form, concentric and radial stimuli Inferior temporal area: Form, pattern recognition V5, Medial temporal area: Motion perception Prefrontal cortex: Facial recognition

27 1. What is the structure of the eye and where are the receptors for light? (continued) 2. How is information about light relayed to the brain? The Visual System 3. What are the major areas of the brain that are associated with the perception of light?