Presentation is loading. Please wait.

Presentation is loading. Please wait.

Exam in 12 days in class assortment of question types including written answers.

Similar presentations


Presentation on theme: "Exam in 12 days in class assortment of question types including written answers."— Presentation transcript:

1 Exam in 12 days in class assortment of question types including written answers

2 Read this article!

3 How does the visual system represent visual information? Brainstorm this: what are the different ways the visual system might encode a feature?

4 How does the visual system represent visual information? Brainstorm this: what are the different ways the visual system might encode a feature? –“labeled lines” many different subnetworks of neurons - activity in a network indicates presence/nature of a feature –spike timing absolute rate or # of spikes per second might indicate presence/nature of a feature “multiplexed” –Hybrid of these two

5 Visual Pathways Themes to notice: –Contralateral nature of visual system –Information is organized: According to spatial location According to features and kinds of information

6 Visual Pathways Image is focused on the retina Fovea is the centre of visual field –highest acuity Peripheral retina receives periphery of visual field –lower acuity –sensitive under low light

7 Visual Pathways Retina has distinct layers

8 Visual Pathways Retina has distinct layers Photoreceptors –Rods and cones respond to different wavelengths

9 Visual Pathways Retina has distinct layers Amacrine and bipolar cells perform “early” processing –converging / diverging input from receptors –lateral inhibition leads to centre/surround receptive fields - first step in shaping “tuning properties” of higher- level neurons

10 Visual Pathways Retina has distinct layers –signals converge onto ganglion cells which send action potentials to the Lateral Geniculate Nucleus (LGN) –two kinds of ganglion cells: Magnocellular and Parvocellular visual information is already being shunted through functionally distinct pathways as it is sent by ganglion cells

11 Visual Pathways visual hemifields project contralaterally –exception: bilateral representation of fovea! Optic nerve splits at optic chiasm about 90 % of fibers project to cortex via LGN about 10 % project through supperior colliculus and pulvinar –but that’s still a lot of fibers! Note: this will be important when we talk about visuospatial attention

12 Visual Pathways Lateral Geniculate Nucleus maintains segregation: –of M and P cells –of left and right eyes P cells project to layers 3 - 6 M cells project to layers 1 and 2


Download ppt "Exam in 12 days in class assortment of question types including written answers."

Similar presentations


Ads by Google