Who Needs Emotions? The Brain Meets the Robot

eware the passionate robot 347
However, this is only the first approximation in unraveling the circuits which
enable the frog to tell predator from prey. Where Lettvin’s group emphasized
retinal fly and enemy detectors, later work emphasized tectal integration
(Grüsser-Cornehls & Grüsser, 1976) and interactive processes involving
the optic tectum and the thalamic pretectal region (Ewert, 1987). Cobas
and Arbib (1992) defined the perceptual and motor schemas involved in prey
catching and predator avoidance in frog and toad, charting how differential
activity in the tectum and pretectum could play upon midbrain mechanisms
to activate the appropriate motor schemas:
Prey capture: orient toward prey, advance, snap, consume
Predator avoidance: orient away from predator, advance
Note that the former includes “special-purpose” motor pattern generators,
those for snapping and ingestion, while the latter uses only “general-purpose”
motor pattern generators for turning and locomotion.
Generic Feature Detectors in Cat Primary Visual Cortex
In 1959, Hubel and Wiesel published “Receptive fields of single neurones in
the cat’s striate cortex.” A whole string of further papers (such as Hubel &
Wiesel, 1962, 1965, 1968; Wiesel & Hubel, 1963; Hubel, Wiesel, & LeVay,
1977) extended the story from cat to monkey, placed the neurophysiology
in an anatomical and developmental framework, and introduced the crucial
notions of orientation and ocular dominance columns in visual cortex—a
cumulative achievement honored with a Nobel Prize in 1981. Where Kuffler
(1953) had characterized retinal ganglion cells in cat as on-center offsurround
and off-center on-surround, Hubel and Wiesel showed that cells
in the primary visual cortex of cat (and monkey) could be classified as “simple”
cortical cells, responsive to edges at a specific orientation in a specific place,
and “complex” cells, which respond to edges of a given orientation in varying
locations. Paralleling the work of Mountcastle and Powell (1959) on
somatosensory cortex, Hubel and Wiesel found that the basic unit of mammalian
visual cortex is the hypercolumn, 1 mm 2 × 2 mm deep. Each such
hypercolumn contains columns responsive to specific orientations. The columns
form an overarching retinotopic map, with fine-grained details such
as orientation available as a “local tag” at each point of the map. Overlaid on
this is the pattern of ocular dominance “columns” (really more like zebra
stripes when viewed across the cortical surface), alternate bands each dominated
by input from a single eye.
How are we to reconcile the “ecologically significant” features extracted
by the frog retina with the far more generic features seen in cats and primates