Week 10 - Behavioral Neuroscience
Week 10 - Behavioral Neuroscience PSYC 4183-001
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This 9 page Class Notes was uploaded by Celine Notetaker on Sunday April 3, 2016. The Class Notes belongs to PSYC 4183-001 at University of Arkansas taught by Nathan Parks in Spring 2015. Since its upload, it has received 30 views. For similar materials see Behavioral Neuroscience in Psychlogy at University of Arkansas.
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Date Created: 04/03/16
Behavioral Neuroscience – Week 10 EXAMPLE QUESTION: A patient in the ER was accidently shot with a nail gun. It is suspected that the nail is lodged in the patient’s brain. What type of structural brain scan should be performed? Why? Answer: CT Scan, MRI would be dangerous since it would cause the nail to move. CT scan will provide the next best imaging besides MRI EXAMPLE QUESTION: What method would you use to measure electrical signals generated during a seizure? ANSWER: EEG EXAMPLE QUESTION: What method would you use to measure the volume of the hippocampus in the healthy human brain? Answer: MRI (it is the ideal way to see an image) EXAMPLE QUESTION: What method would you use to stimulate cortical tissue in the healthy human brain? Answer: TMS Vision The Stimulus The Sensory apparatus Neural Pathways Cortical Representations The Stimulus: Light The human visual system evolved to only be sensitive to the visible spectrum (white light) 1. Visible spectrum = wavelengths of 200 nanometers – 700 nanometers Light varies in wavelength and amplitude • Wavelength primarily affects the perception of color • Amplitude primarily affects the perception of brightness 2. In the natural world, colors are a mixture of multiple wavelengths 3. The purity of the mixture affects the saturation of the color (saturation = color richness) The Sensory Apparatus The Eye 4. Structures within the eye regulate the amount of light and the focus of this light onto the retina 5. The aim in the front of the eye is to get the light in the best exposure and focus possible by the time it hits the back of the eye 6. When it hits the back of the eye it sends the information to the CNS through the optic nerve The Retina: layered structure coating the back of the eye o The critical piece of the eye that receives the light waves and sends information to the CNS o Contains photoreceptors that transduce light into neural signals Has laminar organization Due to the structure of the human eye, light is scattered as it passes through the eye before it actually reaches the photoreceptors where it is converted to neural signals Photoreceptor: Layer of retina that transduces light into neural signal 1. Rods – Night vision 2. Cones – detailed/color vision Rods: Rods operate at low light intensities and are responsible for night vision => scotopic vision If it becomes too bright the rods stop functioning Cones: operate under conditions of daylight and are responsible for detailed vision and the sensation of color => photopic vision 1. S-cones: Short wavelengthsBlue 2. M-cones: Medium WavelengthsGreen 3. L-cones: Long WavelengthsRed Bipolar cells Transfers information from the photoreceptors to ganglion cells Ganglion Cells: Collects information from a set of photoreceptors Axons of Ganglion cells project to the brain via the optic nerve Ganglion Cells Bipolar Cells Photoreceptors Macula: Area of the retina with the greatest concentration of cones Fovea: Area within the macula that contains only cones in very high concentration high acuity vision o There is no vasculature in the fovea so that the light can penetrate straight to the photoreceptors without being scattered by blood vessels Image: Fovea Peripheral Retina – portion of retina outside of the macula poorest acuity Optic Disc – area of retina containing no photoreceptors; this is where the optic nerve and blood vessels exit the retina = blind spot o Your brain has learned to fill this visual information in so you don’t really notice it RODS: Most concentrated in the peripheral retina CONES: Most concentrated in the fovea and macula FUN TIP***If you were stargazing at night and trying to look at a dim star you would not look directly at it (to align with the fovea) you would look a little to the right or left of it so that way you are looking at it with the part of the eye that has the MOST RODS Peak sensitivity for Rods and Cones R= Rods S= s-cones M= m-cones L=l-cones Visual Pathways The retina of each eye receives visual information from both the left and right side of space (left and right hemifields) 7. Contralateral organization 8. If you close one eye you will keep that side of space still because the other eye has both visual spaces. 9. If you cut one optic tract you will lose that one side of space 10. If you cut the optic chiasm you will go blind because that is where the tracts cross so you would lose BOTH sides of space Visual afferents from the retina projects to four structures: 1. Hypothalamus 2. Pretectum 3. Superior colliculus 4. Thalamus (lateral geniculate nucleus) Pathways 1. Retinohypothalamic: projects visual information from the retina to hypothalamus (suprachiasmatic nucleus). o modulates circadian rhythms (sleep cycles) gets you sleeping at night and awake during the day 2. Retinopretectal- A direct projection from retina to pretectum o The pretectum is an area of the midbrain just anterior to the colliculi. o The retinal projection to the pretectum controls the pupillary light reflexWhen there’s less light it relaxes 3. Retinocollicular: Provides visual information to the superior colliculus that is used to control reflexive eye movements. (retina to superior colliculus) o Holds a visual spatial map o This retinocollicular pathway connects to the Parietal Cortex through the Pulvinar Nucleus o Subserves eye movements 4. Retinogeniculostriate: The largest visual pathway, projecting directly to the thalamus (lateral geniculate nucleus, or LGN). o This pathway connects to the primary visual cortex (occipital lobe) o Subserves ALL detailed and conscious vision Retinogeniculostriate Receptive Fields o A cells receptive field is an area where it can receive and process information o A stimulus that DOES NOT fall in the receptive field appears as if there is no stimulus at all o Retina LGN V1 Retina: Retinal ganglion cells have receptive fields with a center-surround configuration Fovea Receptive field = more focused Peripheral Receptive field = more blurry ON CENTER -Designed to pick up a light stimulus on a dark back ground o Spot in center: Light STIMULATES the cells response rate Darkness INHIBITS o Spot in Surrounding area: light INHIBITS the cell Darkness Stimulates If you shined equal amounts of light on both the “on” and “off” area, they would cancel out. OFF CENTER -Designed to pick up a dark stimulus on a light background o Spot in center: Light INHIBITS the cells response darkness STIMULATES o Spot in Surrounding area: light STIMULATES the cells response rate darkness INHIBITS There are also colorsensitive ganglion cells with center-surround organization Receptive fields in the lateral geniculate nucleus are organized in the same manner as retinal ganglion cells, having center-surround configurations Cortical Representations Area V1 Primary visual cortex = V1 = Area 17 = Striate cortex - Function: Small modules that analyze orientation, movement, spatial frequency, retinal disparity, and color. V1 organization - The representation of visual space in V1 has a retinotopic organization - Receptive field selectivity in V1 has a further columnar organization. - Exhibits cortical magnification: There is a greater proportion of cortex devoted to the fovea and macula o Retinotropic: Representation of space from the retina is mapped in an orderly fashion onto the cortex. Most posterior regions represent information from the fovea degrees away from the fovea EXAMPLE QUESTION: The optic nerve is made up of axons originating from____ Answer: Ganglion cells EXAMPLE QUESTION: What Type of photoreceptor are you using to see during the day? Answer: Cones EXAMPLE QUESTION: How would damage to the right optic tract affect vision? Answer: You would lose the left field