Electrographically present and trace conditioned reactions to complex stimuli in man]

In experiments on 48 human subjects aged from 16 to 25 years, elaboration of present reactions to a complex stimulus was accompanied by stabilization of SGR not only in response to the first, triggering, and the last, reinforcing, components of the complex stimulus, but also to its central element provided it was a proprioceptive signal. In addition, SGR magnitude at the moment of the stimuli action was more considerable during the formation of trace processes as compared with one observed during elaboration of present reactions. The results obtained lead to the assumption that reproduction of excitation traces is preceded by the brain estimation of the time equal to the interstimuli pause.     

Human brain evoked potentials and discrimination of short acoustic stimuli with various frequency

We found that the mismatch negativity (MMM) was absent in evoked potentials in passive condition for frequency deviant acoustical stimuli when stimulus duration was only 11-30 ms. But it was shown that it is possible for participants to fairly well discriminate these stimuli and the component N2b in RP was generated without preceding MMN. Processing negativity also was absent in potentials by the minimal stimulus duration (11 ms). Auditory discrimination nevertheless was still possible, but reaction time and number of committed errors increased significantly.     

Physiological and behavioral reactions elicited by simulated and real-life visual and acoustic helicopter stimuli in dairy goats

Background  

Anecdotal reports and a few scientific publications suggest that flyovers of helicopters at low altitude may elicit fear- or anxiety-related behavioral reactions in grazing feral and farm animals. We investigated the behavioral and physiological stress reactions of five individually housed dairy goats to different acoustic and visual stimuli from helicopters and to combinations of these stimuli under controlled environmental (indoor) conditions. The visual stimuli were helicopter animations projected on a large screen in front of the enclosures of the goats. Acoustic and visual stimuli of a tractor were also presented. On the final day of the study the goats were exposed to two flyovers (altitude 50 m and 75 m) of a Chinook helicopter while grazing in a pasture. Salivary cortisol, behavior, and heart rate of the goats were registered before, during and after stimulus presentations.     

Evoked potentials to joint presentation of photic and acoustic stimuli in the human EEG

The results are outlined of a comparative estimation of averaged EP recorded in response to simultaneous and separate presentation of photic and acoustic stimuli on EEG of fifteen healthy subjects and twelve patients with focal lesions of the diencephalic structures. Investigation of the EP components and integral-temporal parameters has revealed that in healthy subjects EP to a combined heteromodal stimulation considerably exceeded by amplitude the one recorded in response to a separate presentation of stimuli. In case of lesion of the diencephalic formations, the converging effect of polysensory stimulation for the main waves of the response was less pronounced than in healthy subjects. At the same time, in pathological cases the summation effect of the afteraction potential (recorded after the main EP components as a slow negative oscillation) was manifested most distinctly, especially in the central zone of the cortex.     

Cell responses to acoustic stimuli in the pterothoracic ganglion of two noctuoid moths

Summary The spike activity of various types of cell responses in the pterothoracic ganglion ofAscalapha odorata (Noctuidae) andEmpyreuma pugione (Arctiidae) was studied. Pure tones (16 kHz forA. odorata and 20 kHz forE. pugione, 45 ms pulses) were presented at a 1 Hz rate over 9 s and at intensities ranging from 25 to 95 dB SPL. The values of the latency period and the interspike intervals allowed us to describe the intensity-latency and intensity-response functions as well as the spike distribution during the responses, the latter being given by the instantaneous frequency, i.e., as the inverse value of the mean of the nine measurements of each interspike interval during the response time. Repeater (RA₁ and RA₂) is a type of cell response that shows a phasic-tonic spike distribution similar to that of the receptor cells (A₁ and A₂) (Fig. 3), but that differs from the latter in a longer (ca. 1.0 ms) latency period, a lower number of spikes per pulse, and a lower instantaneous frequency during the response time (Tables 1 and 2). Another repeater type of cell response (RA) differs from the receptors and the other two repeaters in the form of its intensity-latency function, having the widest dynamic range (from 40 to 50 dB), and exhibiting the highest maximal number of spikes per pulse of all the response types recorded (Fig. 2, Table 1). We recorded also strictly phasic responses (1 or 2 spikes per pulse), which are considered as pulse markers. Of these, one (PM₁ has a shorter latency period (ca. 10 ms) and higher sensitivity than the other (PM₂) (Fig. 4). Two other types of cell responses showed significant differences in their latency period and the number of spikes per pulse under binaural and monoaural stimulation and are assumed to be the consequence of binaural summation, one by inhibition (BSI) and the other by excitation (BSE) (Fig. 5); they also differ in the spike distribution during the response. For the other types of cell responses recorded we used names that reflect the form of their spike distribution: chopper, build, On-S, tonic, and suppression (Figs. 8–12). The spike distributions during the response time recorded in the pterothoracic ganglion of these two noctuoid moths are compared with the temporal patterns of discharge described in the auditory neurons of the first relay stations of birds and mammals. Our results suggest that in the auditory pathway of the two moth species there is divergence, which could facilitate the parallel processing of the sensory information, and convergence, that could play a role in the directional localization of the acoustic signals. The complexity of this central auditory processing in animals with only 2 receptors in each peripheral organ is considerable, and we discuss its possible biological meaning.