Topics Lecture 1:

•   the problem of sensory-motor integration
•   the course program, housekeeping issues
•   assessment - coursework poster
•   perception-action loops: the control of behaviour
•   stabilisation, orientation and navigation
•   control theory, feedback, open and closed loop systems
•   vehicles: from simple control circuits to 'synthetic psychology'

The Problem

Everyday activities like chopping a carrot, driving a car, or playing the piano require precise coordination of sensory and motor systems, produced by our brain continuously and apparently without any particular effort. Inappropriate behavioural control, e.g. in road accidents or in neurological disorders like Parkinson’s disease, demonstrate what kind of, and what amount of information processing is involved in even the simplest activities.

Fundamental aspects of sensory-motor coordination are illustrated by a number of examples from biology, cognitive psychology, neurology and robotics.
The goals of the course are:

• achieve a solid understanding of conceptual frameworks and some essential methods of investigating sensory-motor coordination, and the ability to critically evaluate them
• acquire a comprehensive insight into selected mechanisms that close the perception and action loop
• gain a basic overview over technical solutions (biorobotics) and IT applications (workplace design, VR) related to sensory-motor coordination
• develop an understanding of  the causes and potential therapies of visuo-motor disorders in humans

The program and organisational/formal details can be found at : http://www.pc.rhul.ac.uk/ug-dir/courses/PS306.html

Perception-action loops: the control of behaviour

What information does the brain process, when you make a cup of tea?

• get out of the armchair…

• go to the kitchen (don't bump into furniture, don't fall over the cat)

• find the kettle, check the water, switch it on

• find a cup, a tea bag, put the teabag into the cup

• wait until the water is boiling

• pour the water over the teabag (watch out, don't flood the saucer)

• wait for 2 minutes (do you want milk? -> go for an extra loop!)

• fish for the tea bag, throw it into the bin (avoid a mess on the kitchen top)

• balance the full cup to your armchair and sit down

• sip your tea (and don't burn your tongue)

• enjoy!

Looking at the eye movements of someone making a cup of tea can reveal some of the sensory aspects of these sensory-motor coordination sequence. (Land MF, Mennie N, Rusted J, 1999)

Stabilisation, Orientation and Navigation

a few simple examples of complex but effortless (and mostly unnoticed) brain activities in the coordination of sensory and motor information:

	stabilisation   sailors (and most passengers) stay upright on the boat in strong winds songbirds don't fall of the swinging twig of a bush, hummingbirds hover in mid-air
orientation humans can easily walk along a corridor, or even keep a car on the road bees approach flowers as well as artificial sugar sources bacteria swim towards food sources (nutrient gradients) protista grow towards the light  lobsters navigate in geomagnetic maps (Alerstam 2003)
	navigation you found room 128 this morning, ... ... and will find your way home! whales travel around the world to find specific breeding or feeding waters

you will find many stunning examples of orientation behaviour from the animal kingdom in Waterman (1989).

Feedback, open and closed loop systems

sensory input affects behaviour - behaviour changes sensory input : sensory-motor loop

such loops are formalised in control theory (systems theory); instead of comprehensive mathematical descriptions, which precisely quantify such relationships, we here will only use illustrations in terms of circuit diagrams.

cybernetics: analysing sensory input and feedback connections and using the fundamental control principles to design ‘autonomous’ machines that automatically stabilise, orient, navigate, carry out tasks (one recent goal: autonomous helicopter, click here) 

a simple example - feedback loop for an ocular following reflex :
(much the same circuit could be used to illustrate the control of your heating by means of a thermostat)

if feedback is prevented experimentally (or not used in a particular action component, for instance in saccades), we speak about an open loop (or ballistic) system, as opposed to a closed loop system wich includes feedback about the consequences of the motor action

please note that the reality is less simple: there are many different types of eye movement (motor patterns), interactions with head, body movements, variations in dynamics (the timing aspects of a control system), and several sensory inputs (networks instead of loops)

you can find a bit more about feedback control systems in Houk & Lehman (1987)

Vehicles

the most fundamental principles of sensory-motor control can be incorporated in ‘vehicles’ (Braitenberg, 1984)

the particular, control logic predicts behaviour
a vehicle comprises three basic steps:

• collect information : sensory input of acoustic signals, smell, light, ...
• process information : connections between components & logic of interaction (excitation or inhibition)
• generate behaviour : motor output, for instance in form of simple motors, or articulated limbs, or tools

the simplest possible vehicle has only one sensor, one connection and one motor: its angular orientation is fully determined by external disturbances - it generates a random walk that only can be modulated in its speed, which nevertheless can be used to change the probability of staying inside/outside the area close to a stimulus!

more behavioural variation, in particular directed movements, are possible, when a vehicle is constructed with two sensors (to measure changes of a stimulus) and two motors (allowing controlled rotations)

option 1: sensory stimulation increases motor output: excitation

differential effects of the stimulus on the left/right vehicle motor will lead to changes in speed and direction, depending on the distance from and angle towards the stimulus!

crossed positive connections lead to contralateral excitation >> the vehicle turns towards the stimulus because the closer sensor, which is stimulated more strongly, will increase the thrust on the other side (and vice versa); the vehicle will get faster because detected stimulus intensity, and the magnitude of the motor output, increases when the vehicle gets closer >> ‘aggression’

uncrossed positive connections lead to ipsilateral excitation >> the vehicle turns away from the stimulus because the closer sensor, which is stimulated more strongly, will increase the thrust on the same side (and vice versa); the vehicle will initially get faster because detected stimulus intensity grows, and therefore the magnitude of the motor output increases when the vehicle gets closer; it finally will sit and rest in some distance >> ‘fear’

option 2: sensory stimulation reduces motor output: inhibition

once again, differential effects of the stimulus on the left/right vehicle motor will lead to changes in speed and direction, depending on the distance from and angle towards the stimulus!

uncrossed negative connections lead to ipsilateral inhibition >> the vehicle turns towards the stimulus because the closer sensor, which is stimulated more strongly, will reduce the thrust on the same side (and vice versa); the vehicle will slow down because detected stimulus intensity grows, and therefore the overall motor output is reeduced, speed will diminish when the vehicle gets closer >> ‘blind love’

crossed negative connections lead to contralateral inhibition >> the vehicle turns away from the stimulus because the closer sensor, which is stimulated more strongly, will reduce the thrust on the other side (and vice versa); the vehicle will initially slow down because the overall detected stimulus intensity grows, and therefore the motor output is increased, and in turning away will speed up again and move on >> ‘attentive admiration’

general orientation behaviour : chemotaxis, phonotaxis, phototaxis can be easily explained by such mechanisms

larger sets of sensors & connections can be employed for generating a ‘value system’, more complex vehicles can be designed by additional sensors, action systems, processing strategies

for some moderately complex examples, including groups of vehicles, you can go to:   http://www.cogs.susx.ac.uk/users/christ/popbugs/intro.html

on the other hand, these vehicles (sometimes also called turtles) have found their way into the world of toys, after the robotics community discovered LEGO mindstorms as simple simulation tools, see: http://el.media.mit.edu/logo-foundation/workshops/roboprojects.html

key reading:

• Alerstam, T. (2003) The lobster navigators. Nature  421, 27-28
• Braitenberg, V. (1984) ‘Vehicles - Experiments in Synthetic Psychology’ MIT Press, Cambridge, (152 BRA)
• Bruce, V, Green PR & Georgeson, M (1996) Visual Perception: Physiology, Psychology and Ecology (3^rd ed.) Hove: Psychology Press, (152.14 BRU) (chapters 11, 14)
• Houk, J.C. & Lehman, S. (1987) 'Control Systems: Feedback, Feedforward, and Adaptive Strategies' in: Encyclopedia of neuroscience, edited by George Adelman. Boston : Birkhäuser (612.803 ENC, chapter copy in resources room)
• Land MF, Mennie N, Rusted J (1999) Eye movements and the roles of vision in activities of daily living: making a cup of tea. Perception 28, 1311-1328
• Waterman, T. H. (1989) Animal Navigation. Freeman & Co., New York

some study questions

download lecture handout