Operant conditioning of cortical steady potential responses in rats

Can humans perceive their brain states?

Although the brain enables us to perceive the external world and our body, it remains unknown whether brain processes themselves can be perceived. Brain tissue does not have receptors for its own activity. However, the ability of humans to acquire self-control of brain processes indicates that the perception of these processes may also be achieved by learning. In this study patients learned to control low-frequency components of their EEG: the so-called slow cortical potentials (SCPs). In particular "probe" sessions, the patients estimated the quality of the SCP shift they had produced in the preceding trial. The correspondence between the recorded SCP amplitudes and the subjective estimates increased with training. The ability to perceive the SCPs was related to the ability to control them; this perception was not mediated by peripheral variables such as changes in muscle tonus and cannot be reduced to simple vigilance monitoring. These data provide evidence that humans can learn to perceive the neural activity of their brain. Alternative interpretations are discussed.

Sensory-evoked potentials as indices of neurotoxicity in the rat: effect of 4-tert-butyltoluene

The use of evoked potentials to measure neurotoxicity was evaluated using 4-tert-butyltoluene (TBT) as a test compound. Male Wistar rats were habituated to the recordings of auditory- and flash-evoked potentials until the combined waveform of the evoked potentials reached a steady state. The rats were then divided into three groups and exposed to 0, 50 and 150 ppm TBT for 6 h, and the auditory- and flash-evoked potentials were measured for up to 288 h after exposure. Event-related potentials specifically associated with the temporal pairing of auditory and visual stimuli were not apparent in the recordings. The peak-to-peak values of selected components, integrated amplitude and power spectra of the waveforms in exposed rats were significantly different from control values for at least 288 h in the group exposed to 150 ppm TBT and for 120 h in the group exposed to 50 ppm TBT. It is concluded that evoked potentials may be used for detection and characterization of minor neurofunctional changes due to low-dose exposure to chemicals.

Automatic detection and operant reinforcement of slow potential shifts

A technique for the automatic detection and operant reinforcement of slow potential (SP) changes is described. The SP shift detection device contains 3 inhibit channels to control sources of potential artifact including: vertical EOG, horizontal EOG and high voltage EEG transients. Two EEG SP shift detection circuits allow the simultaneous analysis of positive and negative shifts. The operation and potential uses of the device are discussed.