II. Study Guide for Exam IA. Lecture 14 Sensory Perception and the Visual System1. Be able to list the five different senses and what type of stimuli (light, mechanical forces, chemical signals) they are responsive to.a. Sight or vision  light energy is converted into action potentialsb. Taste or gustation  chemical signals are converted into action potentialsc. Smell or olfaction  chemical signals are converted in action potentialsd. Hearing or audition  mechanical signals (air pressure waves) are converted into action potentialse. Somatosensory  mechanical signals (touch, pressure, pain) are converted into action potentials2. Describe the three different kinds of sensory receptors and what senses they are associated with.a. Photoreceptors  visionb. Chemoreceptors  Olfaction & Gustation c. Mechanoreceptors  audition and Somatosensory 3. Describe the factors influencing receptive field sensitivity and give examples of each.a. Individual receptor sensitivity  different types of receptors have different sensitivities (rods are more light sensitive than cones)b. Density of the receptive field  the total number or receptors in the receptive field 4. Understand how sensory stimulus intensity and stimulus quality are coded or represented in thenervous system.a. The presence of a sensory stimulus is encoded by a change in the number of action potentials fired by the sensory receptor per unit time (the rate of discharge)5. Know the difference in, and be able to define, sensation vs. perception.a. Sensation  the registration of physical stimuli from the environment by sensory receptors (process of sensing our environment through the five different senses)b. Perception  the subjective experience of sensation (how we interpret these sensationsand make sense of things around us)6. Know the factors contributing to perception.a. The nature of the sensationb. Context in which sensory events take placec. Our emotional stated. Past experiences and memories7. Know the difference between the fovea and the blind spot, and specifically how the distribution of rods and/or cones is different in them.a. Fovea  region containing the largest density of photoreceptors; vision is sharpest hereb. Blind spot  region containing no photoreceptors because the sensory neuron axons exit the eye here as the optic nerve8. Be able to compare and contrast rods and cones in terms of their light sensitivity, size/shape, their functions, and what numbers of photopigments they contain.a. Cones are responsive to bright light  responsible for detail, motion, and color; smaller& tapered at end; less sensitive; 3 photopigmentsb. Rods are larger and more numerous and sensitive to dim light  used for night vision; cylindrical; one photopigment9. Know how light is sensed by photopigments—what happens inside photoreceptor cells when light hits them and how does this affect glutamate release? Are photoreceptors hyper-polarizedor depolarized by light?a. Rhodopsin  special pigment molecule in photoreceptors  light strikes it activating a G protein which indirectly closes Na+ channel  less (+) charge flows into the cell and hyperpolarizes it thus decreasing the number of action potentials (brighter the light thefewer the action potentials)10. Be able to list the different neurons involved in the neural relay for the visual system, starting from the photoreceptor and ending in the striate cortex.a. Photoreceptor  bipolar cells  retinal ganglion cells  lateral geniculate nucleus  striate cortex 11. Be able to compare and contrast rods vs. cones in terms of their convergence on bipolar as well as retinal ganglion cells and be able to explain how this fits with their specific functions.a. More rods converge on each bipolar neuron, and more rod bipolar neurons converge on each rod ganglion cell  more convergence makes sense since it means bipolar neurons will activated if any of the rods get activated by light (want rods to more sensitive since they’re sensing dim light)b. Cones are important for fine detail discrimination  so less convergence makes sense if we want a fine map of an objectB. Lecture 15 The Visual System & Visual Processing1. Be able to describe the ventral and the dorsal stream in terms their function and where they send information to.a. Ventral stream & Temporal cortex  object identification; the “what” pathb. Dorsal stream & Parietal cortex  spatial location; the “where” path 2. Be able to describe how the process of line detection takes place by retinal ganglion cells, how line information is summed to provide line detection in the primary visual cortex, and where and how line information converges to provide shape detection in the visual system.a. Retinal ganglion cell receives input from bipolar cells which received input from photoreceptorsb. Each ganglion cell has a discrete receptive field (which is the sum total of photoreceptors) c. Input from several ganglion spot cells is summed and activates a single neuron  ganglion input is translated into lines or bars (different neurons respond to different line orientations)d. Input from many different line neurons in the striate cortex integrates onto single inferior temporal cortical neurons that then process these individual lines into edges or shapes3. Know and be able to describe the 3 different effects of temporal lobe lesions on visual processinga. Visual for agnosia  inability to recognize objects from their shape b. Achromatopsia  inability to detect any colors c. Akinetopsia  inability to perceive movement or moving objects 4. Be able to describe how “where” information is processed in the dorsal stream of the visual system.a. The posterior parietal cortex  received input from the striate cortex via the dorsal streamsb. Also sends and receives input from the motor cortex and then somatosensory cortex that allows us to locate ourselves in space 5. Know the different functions of the dorsal stream and posterior parietal cortex.a. Localization of objects or the body in spaceb. Producing planned movementsc. Spatial memory – remembering where objects are d. Visual attention – follow or tack a moving object visually 6. Know and be able to describe the different effects of posterior parietal lobe lesions on visual functioning.a. Apraxia  inability to execute movementsb. Hemispatial neglect  neglecting one side of the body or visual fieldc.