Abstract: Disclosed are a method and an apparatus for monitoring the brain state of a patient during a medical procedure relative to a self-norm established at an earlier time, when the patient is in a state selected for medical relevance to the planned procedure. To establish the pre-procedure self-norm, electrical measurements are taken of brain functions which are selected for medical relevance to the procedure, and are processed to produce, for each brain function of interest, a respective statistically and medically significant mean and variance. During the procedure, the same brain functions are electrically measured at each of a sequence of time intervals selected for medical relevance to the procedure.

Abstract: An electroencephalographic (EEG) system includes an electroencephalographic instrument comprising a plurality of electrodes adapted to be removably connected to the patient's head to detect brain waves; a plurality of amplifiers, with each amplifier connected to a pair of electrodes; an output multiplexer and a multi-line electrographic recording device, such as a matrix printer, whose display is an on-line display of multi-channel simultaneous wavy lines on a recording medium, such as a strip chart. A digital signal conditioning system is connected between the outputs of the amplifiers and the input of the recording device and functions to minimize misleading effects of muscular artifacts, to detect epileptiform spikes and sharp waves, and to perform quantitative analysis of the EEG signals. This signal conditioning system includes a comparison means which compares analytical features of the patient's brain waves on a statistical basis, with norms stored in a digital storage means.

Abstract: In an electroencephalography system and method, 19 brain wave detection electrodes are removably attached to the scalp of the subject being tested. Using a common reference, such as linked earlobes, each of the electrodes is connected to an amplifier, an analog-to-digital converter and a digital computer, which can be a microprocessor. The digital computer is connected to a magnetic disk or a magnetic tape recorder which records the 19 "monopolar" digitized signals. Subsequently a digital computer will construct any desired electrode derivations, such as derivations from coronal bipolar pairs, sagittal bipolar pairs, or compound electrodes representing a whole hemisphere, by an internal program control. These constructed derivations can be displayed in any desired combination, using a conventional inkwriter or electrostatic matrix printer, or subjected to quantitative analyses.

Abstract: The rapid automatic examination and evaluation of large numbers of subjects by electroencephalography is accomplished by removably securing electrodes to the head of each subject under test to provide a plurality of channels of brain wave information corresponding to different head regions. The brain wave signals are amplified, converted into digital form, and the relative power in each of a plurality of frequency bands for each head region is automatically compared with a set of comparative relative power data derived from a normal population by computing a Z-transform. The results of that comparison are then displayed.

Abstract: In electrophysiology, methods of testing a subject's neural mechanisms of learning and memory in order to quantitatively diagnose the subject's brain dysfunction require specified conditions or stimuli to evoke his electrical brain activity, which are his response or non-response to the stimuli. These evoked responses are quantitatively interpreted by challenges which specify analytic protocol. A test using letter reversal conditions identifies a subject's problems relating to pattern reversal and perception. A test involving figure-ground condition in which a primary stimulus is obscured with secondary stimuli indicates a subject's ipsimodal and cross-modal inhibition. A test using a standard-interruptive condition, in which a series of standard and interruptive stimuli are alternated, indicates a subject's conditionability, sensitization and recovery cycle.

Abstract: A method and system for the quantitative description of human abnormal brain states, for example, to distinguish cerebral death from a barbiturate induced deep coma, includes an electroencephalograph (EEG) system utilizing scalp electrodes and amplifiers. A computer based system controls a multimodal stimulator (clicks, flashes, etc.) to provide evoked response data for different sensory systems. The ongoing EEG and averaged response data are processed quantitatively and compared with previously stored normative data, describing brain states in patients free of head trauma, to calculate a set of Z-transformations. The Z-transformations define Z, the brain state vector (BSV), which may be visually displayed. The length, direction and change of BSV over time provide an evaluation of the anatomical location of any damage, the severity of functional impairment and the rate of improvement or deterioration of the patient's state in order to aid in selection and guidance of treatment.

Abstract: A method in electroencephalography (EEG) for the display of neurometric test data in which electrical activity generated by the brain either spontaneously or in response to specified challenges or conditions is detected at specified locations on the head surface of the subject by a plurality of electrodes. Features extracted from the spontaneous or evoked brain waves are quantified according to specified neurometric indices and categorized, using the mean values and standard deviations of control groups, according to their relative probability in a population of normal healthy people. Multivariate methods such as multiple analysis of variance or stepwise discriminate analysis can be used to identify independent features particularly useful for diagnosis. The values of such features can be used to construct a multivariate vector for each individual patient.

Abstract: Eye and head movements produce large voltages which obscure the electrical activity of the brain, interfering with diagnostic procedures. In the system and method of the present invention electrical response to such movement artifact is detected by a set of electrodes and transmitted to amplifiers, analog-to-digital converters and an on-line to a digital computer. The computer monitors each of the 19 channels corresponding to the 19 electrodes on the subject's head and a pair of electrodes located diagonally above and below one eye (trans-orbital) to detect artifacts associated with eye movement. Each channel of brain waves and artifact signals, converted into digital information, are compared with a threshold selected digital value set by the operator either by using standard values, by empirically eliciting sample artifacts, or by a standard deviation determination. The computer, after determining that there exists a movement artifact, i.e.