CAN, I PHYSIOL PHARMACOL, VOL 68. 1990 Fast path be mous ingle conflict stimulus produces sensory Rectification Slow path Sets overall nausea threshold gain of fast path moral mediation al afference FIG 4 Schematic diagram of revised model for nausea path symptom dynamics. nausea fast path response time(minutes) neural Mismatch 个 gnitude threshold estimate 3 successive 10 min intervals(600s+ 1) slow path response FIG. 5. Mathematical model for nausea path symptom dynamics, Insets show results of a computer simulation their relationship to the threshold element re some followed by a threshold, and not the reverse, as would be the explanation. In the past, many authors have assumed th ase if the linkage were temporary sensory conflict coupling to sympwever, the author has argued or humoral processes that act to continuously accumsnt neural Oman 1982)that some level of subliminal sensory conflict low pass filter or""leaky" integrate) weighted, rectified der or higher block dynamics ays probably consist functionally of dynamic elements are required so that model predictions show characteristic
301 overshoot when the conflict stimulus is tumed off. The slow humoral information transmission. If so, a search for the ath block nom her gain (by a fact the fast path, and at the beginning of notionally th Slow path output act together with other classes of fast-acting nauseogenic inputs Another problem is that until motion sickness researc path response gain. When prolonged stimulation has raised gists to recognize conflict neurons or the sensory mismatch the response of the fast path becomes as shown in the Fig. 5 simulation. Thus, the Based on the discussion in previous sections, we can suggest revised model mimics the much magnified response to incre. the following ()Conflict signals are emor signals in CNS control creased response sensitivity at high symptom levels was a is probably neural and conveys relatively hig consequence only of uc at the output of the model. This signed information conceming the instantaneous differenc The fast and slow dynamic elements in the model presum. within the visual and (or) proprioceptive sensory modalities as linkage mecha his s or the dy namer prp ernies of the emetic during normai aetive mo vements and moment anly large when hemselves. The dynamic operators may approximate unexpected obstacles or disturbance forces are briefly encoun- oral conflict ocess can be driven experimentally, conflict signals shoul signal stimulation. For example, vestibular conflict neurons produce behaviors suggestive of disorientation and may trigger might work in synergistic pairs, somewhat as vestibular affer- processes should trigger neuron activ atory and had the character that a burst produce prolonged sensory conflict and symptoms. Sensory produced a prolonged (e. g, I min) rism goggles ould produce cor et al.( 1990)have desc class of AP neurons sensory-motor leaming proceeds via intemal model updating pplied neurotransmitter agents. They attribute the long lasting signal)probably play some causal role in triggering sensor size of sensory conflict signals ed to previous sensory-motor experience under culating from the hypothalamus-pituitary or opposite sign should be moved, increased conflict signals of haracterized bs mu h slo er re sponse ti me s, Tshis e the kinde prob Eyheae l le et sit oans onat et of physiological mechanisms that might be involved ecause their functional effect could be distributed along Conclusions (iii)The nts the putative com n forms of motion sickness. ccumng in va ensor modalities. The aller ong circumstantial evidence neurally coded. It should increase in of the sign of the associated conflict. If dynamics of the fast and slow path mechanisms originate in or the emetic linkage process. The sea a "conflict ossible to directly ch has been largely sponding to the neural mismatch signal but only signals cor the vestibulo -ocul responding of st and slow embic system are t ex pe ime for spatial orientatilonentarmn. The model presented here captures many of However the signals are probably neurally coded, as discussed in the be noted, The model posits an observer that is ma previous section, conflict linkage mechanisms may involve linear. Although recent experimental data certainl
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