Electrocorticogram and sensory evoked potentials in the young hydrocephalic H-Tx rat.

The ECoG and the sensory evoked potential in response to stimulation of the contralateral forelimb were studied in control and hydrocephalic H-Tx rats between 21 and 35 days of age by recording in several positions from the dura overlying the somatosensory cortex. All hydrocephalics showed longer periods of low amplitude, high frequency ECoG activity than the controls. For the evoked potentials the hydrocephalic rats were divided into two groups: those that gave an evoked potential in at least one electrode position and those that did not give any evoked potentials. In the hydrocephalic rats that gave an evoked response the latency of the fourth phase of the evoked potential (the N2 component) was significantly longer than in the control rats suggesting that the processing of the signal within the cortex was affected by the hydrocephalus. The absence of an evoked potential in some hydrocephalic rats suggests there may be a disruption of the thalamo-cortical pathway preventing the response from reaching the cortex.