METHOD AND APPARATUS FOR ESTIMATING A COGNITIVE DECISION MADE IN RESPONSE TO A KNOWN STIMULUS FROM THE CORRESPONDING SINGLE-EVENT EVOKED CEREBRAL POTENTIAL

The present invention estimates the cognitive decision made in response to a known stimulus from the corresponding single-event evoked cerebral potential. The present invention uses a unique recursive procedure to identify the decision from a mathematical description of the potential as the output of a cerebrally located, autoregressive, moving average filter with the stimulus as an exogenous input. The procedure employs in a two-step sequence, the least squares algorithm to update the filter coefficients, followed by a Taylor's Series approximation for updating an internal cerebral source signal which is generated in response to the external stimulus. The recursive procedure computes the attenuation used by the moving average component of the filter to produce the cerebral source signal. This procedure is repeated for all feasible cerebral source signals, computed from the set of possible event evoked average response potentials, to produce a set of attenuator-values. These values are then used as input to a multiple-layered, feed-forward artificial neural network for identifying the decision made from the set of feasible responses. In turn, the power spectrum computed from the autoregressive coefficients is used to track the cognitive state and therefore the reliability of the decision estimate. The present invention may be used for the control by mental thought of computerized visual and aural display functions, by measuring the electroencephalogram in time with the operant orientation of the user onto a displayed stimulus.