ABOUT THE DEPARTMENT OF NEUROPHYSIOLOGY TILL 1969– INVESTIGATIONS IN THE FIELD OF PHYSIOLOGY OF THE BRAIN
from the occasional publication „50th Anniversary of the Nencki Institute”
A small laboratory of neurophysiology was established in the Nencki Institute in 1933 and in the post-war period it was transformed into a separate department. This Department is concerned with brain physiology on the one hand and with biophysics and biochemistry of the nerve fibres on the other.
In the pre-war period Miller and Konorski began and carried out their work on instrumental (type II) conditioned reflexes (CRs) and their interrelations with the classical (type I) CRs. These authors distinguished four varieties of type II CRs. In the first variety the animal performs movement M in response to a CS, when the compound CS + M is reinforced by an attractive unconditioned stimulus (US+), while CS alone is not reinforced. In the second variety the animal inhibits movement M in response to a CS, when the compound CS + M is reinforced by an aversive US (US—), while CS alone is not reinforced. In the third variety the animal inhibits movement M in response to a CS, when CS alone is reinforced by US+ and CS + M is not. In the fourth variety the animal performs movement M to a CS when CS alone is reinforced by US- and CS + M is not. Konorski and Miller performed experiments in which each of these varieties was represented and their properties were examined.
In the post-war period the studies on type II conditioned reflexes were continued in our Department and the following basic principles concerning this conditioning were discovered:
- The type II CR may be formed only from the reflex motor acts, that is from those acts which occur by the intermediary of the CNS. The purely passive movements and the movements evoked by stimulation of the motor area of the cortex cannot become type II conditioned responses.
- The indispensable condition for the formation of the type II CR is that the motor act be performed against the background of a definite drive and that after its performeance the drive be reduced; this reduction is accomplished by inhibition of hunger drive, when the food is placed in the mouth, or by cessation of the fear-producing stimulus.
- The type II CR is formed and produced by the joint action of connections running directly from the CS center to the kinesthetic center of the movement and form the drive center to the kinesthetic center (Fig. 1). Connections running from the CS center to the kinesthetic center determine the movement to be performed, whereas connections running from the drive center to the kinesthetic center release the movement determined by the former connections.
- The proprioceptive feedback of a motor act is in principle not indispensable either for the formation of an instrumental response from this act, or for its execution, since the type II CR may be formed or preserved after deafferentation of the limb involved.
Another line of research has been concerned with the problem of the so called internal inhibition and transformations of CRs. It was found that a stimulus presented without a reinforcing agent among positive CSs acquires strong inhibitory properties with regard to that agent. It is hypothesized that this stimulus becomes a Cs signalling no-US, and as such it is antagonistic to a CS signalling the presentation of the US. In this way the extinction of a CR by non-reinforcement of the appropriate CS may be regarded as a transformation of the positive CR into the negative one, and it obeys the same rules as those obeyed in transformations of heterogenous CRs.
A great part of the research work performed in the Department is concerned with the problems of functional organization of particular regions in the brain. Much work was done on the function of the prefrontal area. It has been established that lesions in this area may produce the following behavioral disorders:
- disinhibition of inhibitory alimentary CRs,
- impairment of delayed responses, and
- „magneto-reaction” consisting in strong directional response to the source of a CS. It seems that these symptoms are independent from one another and are produced by a different placement of lesions.
Studies on the functional role of the sensori-motor cortex led to a conclusion that this region is important for a technical aspect of the execution of the learned motor act, but not for its programming. It seems that this programming is accomplished by the caudate nucleus with regard to simple movements and by the pre— motor cortex with regard to complex movements.
A great deal of work was performed on the functional role of the emotive brain and in particular of the hypothalamus and amygdala. Experimental data show that these two structures are concerned with various drives, and in particular with hunger, fear and anger. There is some evidence to show that the centres controlling particular drives consist of two sub-centers, one being concerned with excitation of the drive, and the other being concerned with its inhibition on satisfaction Since, as stated before, instrumental CRs are produced by reduction of appropriate drives, there is a close relation between stimulation or removal of particular parts of the emotive brain and instrumental responding.
The study devoted to the problem of plasticity of URs led to the conclusion that the intensity of these reflexes changes considerably with their mere repetition: some of them tend to increase by repeated elicitation, others on the contrary tend to decrease and even disappear.
In recent years two important lines of investigation have been started in the Department, namely the study of the function of the isolated waking brain obtained by midpontine incision, and the study of functional properties of the visual system.