What Is an Evoked Potential?

The body's self-generating activity can be affected by direct or external deterministic stimuli (electric, light, sound, and other stimuli). Another localized potential change is called evoked potential. Also called evoked response, event-related potential.

The body's self-generating activity can be affected by direct or external deterministic stimuli (electric, light, sound, and other stimuli). Another localized potential change is called evoked potential. Also called evoked response, event-related potential.

Chinese name

Evoked potential

Foreign name

Evoked Potential

Also known as

Evoked response

Irritate

Sound, light or somatosensory stimulation

Definition

Weak electrical changes in the human brain

feature

1. Must be detected at a specific location;

2. Has its specific waveform and potential distribution;

3. There is a strict time-locked relationship between the latency of evoked potential and stimulation, which appears almost immediately or instantaneously within a certain time when the stimulation is given.

Evoked potential classification

Different sensory evoked potentials are different, and the differences in stimulation characteristics are also reflected in the waveform structure of the evoked potentials.

Visual evoked potentials usually consist of 8 repeatable components. These ingredients are relatively stable, reliable, and have obvious common characteristics among individuals. The twins have more similar visual evoked potential patterns. The brightness, frequency, and motion of visual stimuli have specific effects on visual evoked responses. Increasing the intensity of the stimulus shortens the incubation period (mainly components after 500 milliseconds) and increases its amplitude. The waveforms of evoked potentials caused by different wavelengths of light stimulation are also different. Subjects with normal color vision had different pattern evoked potentials for the brightness difference and hue difference of visual stimuli respectively; color blind subjects only had specific pattern responses to brightness differences, but no specific pattern response to hue differences.

Auditory evoked potential A short acoustic evoked potential is a wave group consisting of 15 components. According to the length of the incubation period of each component, it can be divided into early, middle and late groups. The six components (named ) with a latency of less than 8 milliseconds are the early component groups, which are the activation responses of the cochlea and brainstem auditory nucleus; P o, N a, P a, N b,), which represent the activation of thalamus-related auditory parts and the cerebral cortex, may also be intermixed with disturbances in the electrical activity of the scalp muscles; long latency components (named P 1, N 1, P2 , N2 , ...) occur after 50 milliseconds of stimulation and are often referred to as late components. The evoked potential caused by the use of speech sounds is asymmetric in left and right hemispheres.

The early component of the body evoked potential represents the exact time when the incoming signal reaches the parietal area of the cerebral cortex. This negative phase wave is a large duration N 1 wave in the newborn. From the newborn to 8 years old, it gradually changes to a pattern close to that of an adult. This early component negative wave can be repeated in individuals of the same age and can be used as an important indicator of infant brain development. In the blind, the latency period of the body-evoked response is shorter than that of the normal person. The latency of the late component of the normal person is 150 milliseconds, and the average time of the blind is 20 milliseconds earlier.

Event-related slow potential

Evoked potentials involving psychological factors. It includes late components, dependent potentials, and exercise-related potentials.

Late components mainly include positive and negative potentials within 200 to 500 milliseconds, usually named according to the polarity and latency of their main components. For example, a positive wave with a latency of about 300 milliseconds is named P 3 or P 300, which is called a late positive wave. The late component is related to the information process, so it is also called "information-related potential". Psychological factors related to late components include signal meaning, information application, orientation, suppression, selective cognition and awareness. The late component is more clearly recorded at the cranial and frontal regions, and it is not related to the sensory characteristics of the stimulus but a brain activity event.

The maximum amplitude of the late component is usually in the parietal lobe, and under certain conditions, such as when the subject is required to change the preset plan, it can also be recorded in the forehead area. Because the late potential is not a uniform component but includes several positive and negative waves, its origin varies from operation to operation. Most of the late components of the study are distributed in the posterior region of the brain, while the positive potential components of the new stimulus after the negative direction wave are in the frontal region. It can be envisaged that the different regional distributions of late components may reflect the different functions of the cortical and subcortical sites on neostimulation and information processes.

The substantial increase in the late component is related to the amount of information carried by the stimulus, which can be explained by some psychological activities, such as making decisions, cognitive evaluation, sample matching, decreased arousal, impermanent stimuli, preset changes, and selective attention. In addition, late components are often caused by new, rare, or unexpected stimuli. This is related to the so-called orientation response concept. Therefore, late components are not a single phenomenon, but include multiple components. Each component may be related to the behavior of perception. Different aspects are relevant.

The slow potential change between two successive stimuli that occur at the baseline of the EEG with the causal potential (CP), that is, the predictive signal and the action signal, was discovered by WG Walter. The most significant of these is the CNV. The specific condition of CNV is to give a notice signal (S1, conditional stimulus) to the subject before the commanded stimulus (S2, action signal) to perform a certain task, and the two stimuli are separated by 1-2 seconds. 200 ms after the first stimulus was applied, and continued to the end of the action response of the second stimulus, there was a negative phase slow potential change in the cortex, namely CNV. Its amplitude is about 10-50 microvolts, and it is a reliable slow change of evoked potential, which can usually be recorded from the central area and frontal area of normal people. CNV is generally considered to be related to anticipation, motivation, motivation, learning and attention. The study also found that the magnitude of the potential is proportional to the magnitude of the force required to anticipate the response; the magnitude change is also proportional to the speed of movement of the expected response S2. When the response action can end S2 and can avoid electric shock, CNV telecommunication improves significantly. These results show that dynamic state and reaction intention are important for the development of CNV. Attention is closely related to the development of CNV. The amplitude of CNV is often weakened by external stimuli, such as talking, reading, irrelevant tones, and basic music. Both of these results may be interpreted as a distraction effect on CNV and supportive assumptions about CNV development. CNV is a valuable reference diagnostic tool in psychiatry. The development of CNV in anxious patients is slow, and the amplitude is small and unstable. Patients with obsessive-compulsive perception have high CNV amplitudes and cannot easily return to baseline. The duration of CNV in patients with schizophrenia is longer and the magnitude is smaller.

Slow potential changes in the brain before and after autonomous movement of motor-related potentials. Exercise-related potentials can be divided into 4 components: N 1, a slowly rising negative potential, commonly referred to as the preparation potential (BP), or the preparation potential (RP); P 1, an unsteady small positive wave; N 2 , Fast phase negative potential; P 2, large and slow positive wave. Preparatory potentials are similar to random potentials, but they are related to different psychophysiological mechanisms and are different in amplitude, shape, and distribution.

Time program

Generally speaking, evoked potentials can be divided into two main time programs, primary response (early response) and post-primary response (late response).

The earliest part of the primary response was through the specific thalamus cortex pathway to reach the first cortical sensory region. The late response, which arrives at 50 to 100 milliseconds after stimulation, is emitted through neurons in the extramedullary channel, and its pathways include a reticular structure and a non-specific thalamus nucleus. Late reactions are widely distributed on both sides of the cortex and are affected by changes in consciousness. Thus, early responses are functionally related to sensory acceptance, while late responses are related to information processes.