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Melior Discovery neurophysiology

Cortical Sensory Evoked Potentials
Somatosensory (tibial n., auditory, etc.) evoked or event-related potentials can be recorded at various locations in the brains of rats and mice using surface or depth electrodes.  These potentials can be used to monitor the effects of drugs on attentional and cognitive functions.  Auditory evoked potentials have been recorded from the hippocampus, for example, to evaluate the effects of drugs on attention.  A topographic map of EEG responses to auditory clicks shows functional localization of responses across the cortex.

Figure A- Illustration of Depth Electrode in Hippocampus:

                                  

Illustration of bipolar depth electrode implanted into the CA3 region of the hippocampus. 

 

Figure B- ERP, Conditioning Versus Test Tone:

                            

Hippocampal evoked responses to an auditory conditioning tone (blue) followed 0.5 seconds later by a test tone (red) (tones = 3 kHz x 10 msec duration).  Tone-pairs were delivered 10 seconds apart; n=24. The test tone amplitude  (P1-N1) was reduced by approximately 50% compared tot he conditioning tone. 

 

Figure C- Auditory Evoked Potentials: Topographic Mapping:

                              

The figure above shows average evoked responses from a rat implanted with 12 separate chronic supra-dural electrodes using a common reference over the olfactory bulb.  Responses to auditory clicks (75 dB, 10 msec, 3 kHz, 11 sec ISI, n=32) from a speaker above the animal are shown adjacent to electrode position.  The largest response, at location "RFR" (right fronto-parietal region), was above the auditory cortex.  Note the different shapes of potentials around this location indicating localized surface responses.  Time scale at the bottom in msec; tone at time 0. 

 

If you are interested in learning more about Cortical Sensory Evoked Potentials, please contact models@meliordiscovery.com to start the conversation.