**4. Lateral orbitofrontal loop**

The lateral orbitofrontal circuit takes part in initiating social behaviours motivated by an award and in inhibiting behaviours, which can trigger punishment (Royall et all., 2002). Incorrect functioning of this circuit may result in disinhibition of behaviours, personality changes, lack of control and emotional liability, as well as irritability and gaiety (DeLong & Wichmann, 2007). The damage of this loop can cause perseverations, which make it difficult to process information from external environment and adaptation of behaviours to a particular situation (Royall et all., 2002).

Functional Anatomy, Physiology and Clinical Aspects of Basal Ganglia 97

The direct pathway is connected with striatal medium spiny neurons (ENK) secreting GABA and it leads through the external part of the globus pallidus (GPe) to STN, which stimulates inhibitory neurons in GPi and SNr structures. Cortico-striatal stimulation of the indirect pathway decreases thalamus stimulations and inhibits motor cerebral cortex (Albin et all., 1989; DeLong, 1990; Obeso et all., 1997, 2000b; Herrero et all., 2002; Sobstyl et all.,

Dopamine is a neurotransmitter in SNc neurons (Groenewegen, 2003; Sobstyl et all., 2003; Groenewegen & van Dongen, 2007). During repose occasional discharges of small frequency, which do not affect movement, appear in these neurons (Longstaff, 2006). The frequency of neurons firing changes when a stimulus rewarding a movement is present (ibid.). They influence the reply of striatal medium spiny neurons to the stimulation from the cerebral cortex. GABA/SP/DYN neurons increase responsiveness in the direct pathway, however GABA/ENK neurons reduce responsiveness in the indirect pathway due to the SNc influence. As a result, the nigro-striatal connection increases the activity of the direct

The basal ganglia are responsible, inter alia, for executing motor sequences (Alexander et all., 1990; Mink, 1999; Sadowski, 2001; Herrero et all., 2002; McFarland et all., 2002; Longstaff, 2006; Haber et all., 2009). Each sequence is represented by striatal medium spiny neurons creating motor or oculomotor microloops in the cortico-subcortical circuit, which can be activated or inhibited (Alexander et all., 1986; Longstaff, 2006). A considerable part of striatal medium spiny neurons has low frequency of electric discharge at rest (0,1-1Hz). In other subcortical nuclei - GPi and SNr, the frequency of electric discharge at rest is considerably higher and it amounts to about 100*Hz* (ibid.). According to a contemporary model of motor control carried out by the basal ganglia, movements are initiated by activation of the motor cerebral cortex, which consequently activates the striatum (Groenewegen, 2003; Sobstyl et all., 2003; Longstaff, 2006; Groenewegen & van Dongen, 2007; Sadikot et all., 2009). The activity of striatal medium spiny neurons increases during the execution of movements being a result of functioning of cortico-striatal neurons (Longstaff, 2006). When a discharge frequency of GPi and SNr decreases, a reduction in the thalamus inhibition follows making it possible to execute a movement or other mental action (Albin et all., 1989; DeLong et all., 1990; Obeso et all., 1997, 2000; Sobstyl et all., 2003;

Motor, emotional and cognitive functions are controlled by the system of structures and connections of the central nervous system, among which three levels of co-operation were distinguished: lower, middle and upper (Schotland & Rymer, 1993; Longstaff, 2006). Experimentally induced damages of the nervous system centers in animals result in the lack of the function subjected to the place of the damage and the appearance of new or enhancement of until now executed actions. A damage of the motor center of the cerebral cortex causes limbs paresis, an increase in muscles tension, intensification of tendinous reflexes in these limbs as well as appearance of Babiński's reflex (Babinski, 1986). The occurrence of such symptoms indicates that lower in hierarchy structures are inhibited by higher ones and that the lack of this inhibition causes unblocking of the physiologically inhibited centre. Clinical observations of persons with the basal ganglia damages indicate that these structures do not initiate movements, but they control the course of skilled sequence of movements (ibid.). An increase in the activity of the direct pathway increases, and of the indirect pathway decreases, stimulation of particular areas of the cerebral cortex (Groenewegen, 2003; Longstaff, 2006; Groenewegen & van Dongen, 2007; Szołna, 2007).

2003; Longstaff, 2006; Groenewegen & van Dongen, 2007).

pathway, inhibiting the indirect pathway (ibid.).

Longstaff, 2006).
