What is the initial waveform recorded of a near-field potential?

The initial waveform recorded of a near-field potential is characterized by a positive deflection, which occurs as a result of electrotonic depolarization of the membrane beneath the recording electrode. Near-field potentials are typically observed close to the source of neural activity, such as at the axon or dendrites, where the electrical activity leads to localized changes in the membrane potential.

When a neuron fires, the influx of ions during action potentials causes a local depolarization. This brief increase in positive charge relative to surrounding areas generates an electrotonic field, which can be detected by electrodes placed nearby. The recording reflects these initial changes in membrane potential, resulting in a positive deflection on the waveform. This phenomenon is critical for intraoperative monitoring as it serves as an indicator of neuronal activity and health during surgical procedures.

The other choices do not accurately describe the physiological response during near-field potential recording. A negative waveform would imply hyperpolarization, which is not typical upon initial depolarization events. A flatline indicates no response, leading to a lack of measured activity, contrary to the expected response when detecting near-field potentials. A random waveform would suggest interference or noise rather than the specific, coherent signals expected from near-field activity.