A human parietal face area contains aligned headcentered visual and tactile maps

1
A human parietal face area contains aligned
head-centered visual and tactile maps Sereno
Huang (2006)
2

• Topographic relationship between position of
  sensory receptor and position of neuron in grey
  matter sheet
• Superior parietal cortex
• Somatosensory position on face
• Visual positions close to face
• Alignment of the two topographies
• Is the visual topography independent of eye
  position?
• Do we calculate a visual map of the world with
  eye position subtracted?
• Such a map might influence our perception

3
Retinotopy - eccentricity
4
Retinotopy polar angle
5
Transforming between topographies from different
modalities

• The origin of the auditory sensory space is the
  head
• The origin of visual sensory space is the fovea
• Superior colliculus contains an auditory map
  converted to have a visual sensory origin
  (retinotopic)
• Enables saccades to auditory targets
• LIP in parietal cortex is similar

6

• Colour on diagram changes with polar angle
• These colours are mapped onto cortex
• Air puff locations correspond to visual locations

7
Summary of main conditions

• Air puff left face versus right face
• Air puff polar angle mapping (eyes shut or fixate
  central)
• Visual polar angle map using rotating wedge of
  Xena movie (fixate central)
• No reason given why simpler stimulus is
  inappropriate
• 100 deg field of view why?
• Depth cues indicate near visual stimulus for
  correspondance to facial location (no distant
  control)
• Was it really necessary?
• This matches some monkey work
• But other studies on human VIP use distant
  optic flow and assign the function of heading
  perception
• VIP may well be VIP
• Visual polar angle map Xena (eyes track
  stimulus)

8
25 deg
9

• Face puffs activate S1 and superior parietal
  focus
• Structured motion activates occipital plus
  superior parietal focus

10

• Alignment of somatotopy and retinotopy
• Single subject
• Polar angle maps
• Alignment good or not so good?
• Alignment index?

11

• Average of 9 subjects
• Top two views dorsolateral
• Bottom view lateral
• How good is the alignment?

12
Gaze-o-topy

• Does this exist?
• Is there any systematic periodic response to the
  circular diagram I showed earlier?
• If it does exist, is it aligned in the cortex
  with the somatotopic (air puff) map?

13
1 shown (but only 2 in total) Reasonable alignment
14

• Tabulated alignment between different mapping
  experiments
• Not clear what the alignment index measures
• Why does the correlation not always agree with
  the index?
• Only 2 subjects for gaze-o-topy, and one of those
  has low correlation

15
Possible roles for the gaze independent map of
visual space

• Sereno
• Approaching and manipulating objects with the
  face
• If we consider the VIP heading tradition (CUBIC
  scanner studies!)
• Detects collisions under conditions of linear
  self and object motion via the simple cue that
  the collision event will not move location on the
  map, whereas other objects will
• And gives the incoming trajectory of the
  collision enabling its avoidance
• Can this be done with retinal flow patterns
  confounded by eye movement?

16
Verdict?

• Gaze independent visual maps would potentially be
  useful, and could also be a mechanism for visual
  stability.
• However, the evidence presented here is weak, and
  there is much more data about the reverse
  remapping process, e.g. superior colliculus.