1. Sensory systems

2. What do sensory systems do? Information about the world Each system responds in a specific way to a stimulus They use specialized cells, peripheral receptors Transduce the energy –Into a change in membrane potential – Represent stimulus in a signal that all neurons can use: –Same currency, action potentials

3. Different stimulus energies ( Platypus )

4. Different stimulus energies ( Platypus ) Electroreception through sensitive bill

5. Different stimulus qualities ( Bees, dolphins ) Separate groups of neurons Constantly updating

7. Rubin vase Interaction between Ascending, stimulus-driven Descending, goal-oriented (Focusing attention) This interplay shows: Difference between sensation and perception

8. Sensory neurons signal events using… Rate codes (stimulus intensity) Spatial codes (stimulus density, acuity) Temporal codes (stimulus frequency)

9. Psychophysics The quantitative relationship between a stimulus and a sensation A typical sigmoid function

10. Neuroscience in the 21 st century: Connecting psychophysical measures to neural activity Work by Bill Newsome, Mike Shadlen, etc. e.g. Motion coherence stimuli

11. Neuroscience in the 21 st century: Connecting psychophysical measures to neural activity Work by Bill Newsome, Mike Shadlen, etc. e.g. Motion coherence stimuli

12. Neuroscience in the 21 st century: Connecting psychophysical measures to neural activity Work by Bill Newsome, Mike Shadlen, etc. e.g. Motion coherence stimuli

13. Effect of motion coherence on behaviour Effect of motion coherence on neural activity Neuroscience in the 21 st century: Connecting psychophysical measures to neural activity

14. Effect of motion coherence on behaviour Effect of motion coherence on neural activity Neuroscience in the 21 st century: Connecting psychophysical measures to neural activity

15. Sensory neurons Get from physical energy to action potentials

16. Receptors Specific for a narrow range of input Vary across sensory systems All lead to a change in membrane voltage –photoreceptors: closure of Na + channels hyperpolarizing –mechanoreceptors: opening of Na + channels depolarizing

18. Common anatomical plan Cross the midline on the way to thalamus (To modality-specific thalamic nuclei) And then onto primary sensory areas Six layers III and IV receive axons from thalamus (granular cortex) From layers III and IV, projections onto other layers II: Ipsilateral (feed forward) III: Contralateral (unified percept) V: Spinal cord etc. (motor control) VI: Back to thalamus (focusing)