of the 26th Goettingen Neurobiology Conf. 1998 Vol 1
Ed: Norbert Elsner & Ruediger Wehner
Georg Thieme, Stuttgart, N.Y.
and Cognition: From fish to hominids
Movement is the first product of the nervous System
- is it also its last riddle?
Vertebrate behaviour and cognition seem to have originated in fish.
Every movement of the tail of a fish or of its fins will change
the position of the fish in (relation to) its environment. These
changes are received by the sense organs: locomotion produces locosensation.
Or in the words of Ragnar Granit: "Muscle moves the world".
Not only our first ancestors were mobile, so, too, were their first
life-essential objects: prey, partners, competitors and, perhaps,
predators. The cognition of fish has to take note of three moving
bodies: itself, its shifting environment and the other animal. The
nervous system produces (rhythmic) motor patterns and perceives
environmental changes according to these patterns ( figure A).
The next step towards mankind were the tetrapodes. As with
fish, their eyes continue to scan the horizon, but the direction
of their (loco)motor activity has bent by 90° ( figure B). Reafferent
information's are coming from the limbs, additionally. The importance
of this internal feedback is that body parts can now move without
influencing the environment. Locomotor patterns are thus "fed
back" via exafferent patterns (environment shift) and via reafferent
Primates have four hands to make contact with the arboricole
environment. They prefer to sit, moving their arms freely to reach
and grasp. Their locomotor apparatus has begun to split:
While seated, the hind limbs and the pelvis are engaged in "nonlocomotion",
but the arms and hands bend again by 90° and appear in the frontal
visual field (actually this bend developed between head and neck,
For the first time in the evolutionary process, animals can watch
directly and for extended periods of time what parts of their body
are doing. Arm and hand motor patterns are also sensed twice: By
reafference and by the newly possible visual control. When the nervous
system takes notice of the synchronicity in this closed motor-visual
loop, the eye-hand complex can develop. Does this indicate that
hands, objects which hitherto were known only as parts of the environment,
have been "recognised" as parts of the subject? Can we
assume that "self- recognition" has taken place?
In hominids the eye-hand-complex permanently works in an
autonomous manner. Even during locomotion, arm and hand movements
are "movements of their own", independent of the actions
of the hind limbs. Tools are now endowed with self-moved quality,
throwing extends the distance reachable, the individual can recognise
his own shadow and perhaps also his own face moving in a smooth
surface of water.