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Ch. 14: The Cutaneous Senses

Ch. 14: The Cutaneous Senses. PP. 334-339. Plasticity of Cortical Maps. Figure d14.5: Somatosensory cortex. Cortical organization. Experience-dependent plasticity Similar to Auditory system: training owl monkeys to discriminate between frequencies.

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Ch. 14: The Cutaneous Senses

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  1. Ch. 14:The Cutaneous Senses PP. 334-339

  2. Plasticity of Cortical Maps Figure d14.5: Somatosensory cortex Cortical organization Experience-dependent plasticity Similar to Auditory system: training owl monkeys to discriminate between frequencies. William Jenkins & Michael Merzenich (1987)

  3. Perceiving Details • Measuring tactile acuity: Brial reading • Two-point threshold - minimum separation needed between two points to perceive them as two entities • Grating acuity - placing a grooved stimulus on the skin and asking the person to indicate the orientation of the grating • Raised pattern identification –using such patterns to determine the smallest size that can be identified

  4. Receptor Mechanisms for Tactile Acuity • There is a high density of Merkel receptors (SA1) in the fingertips. • Merkel receptors: densely packed on the fingertips (similar to cones in the fovea)

  5. Cortical Mechanisms for Tactile Acuity • Body areas w/high acuity have larger areas of cortical tissue • Receptor field for neuron in cutaneous system parallels receptive field for visual system . • Areas with higher acuity have smaller receptive fields on the skin.

  6. Perceiving Vibration • Pacinian corpuscle (PC) is primarily responsible for sensing vibration. • PC’s nerve fibers respond best to high rates of vibrationthan low rates. • The structure of the PC: responsible for the response to vibration & fibers without the PC respond only to continuous pressure.

  7. Perceiving Texture • Katz (1925) suggested: perception of texture depends on two cues • Spatial cues are determined by the size, shape, and distribution of surface elements. • Temporal cues are determined by the rate of vibration as skin is moved across finely textured surfaces. • Two types of receptors may be responsible for the duplex theory of texture perception

  8. Perceiving Texture . • Hollinsand Reisner (2000) shows support for the role of temporal cues. • To detect differences between fine textures, participants needed to move their fingers across the surface.

  9. Adapting Stimulus • Hollins used selective adaptation procedure • Two conditions: 10Hz & 250Hz • Results: condition 250Hz could not detect texture difference after a while

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