Transduction is the process by which, upon exposure to a stimulus, a receptor cell converts that energy or substance into a change in the electrical potential across its membrane. Receptor cells are transducers that convert energy around us into neural activity that leads to sensory perception.

Transduction

Sensory adaptation is the process by which conscious perception of a stimulus decreases over time due to constant exposure. By demonstrating that continuous sensory input does not always reach awareness, it serves as a key concept to help explain the difference between what is merely sensed and what is actually perceived.

Sensory Adaptation

Also known as top-down processes, neural connections descend from the brain to lower stations in the sensory pathway, in some cases as far as the receptor surface. In this top-down process, the upper brain regions modulate the activity of lower centers.

Control of Receptor Cells from Upper Levels

The receptive field of a sensory neuron consists of a region of space in which a stimulus will alter that neuron's firing rate. To determine a receptive field of a receptor cell, one must record the neuron's electrical responses to a variety of stimuli to see what makes the activity of the cell change from its resting rate. 

Receptive Fields

Tonic sensory input adapts slowly to stimuli and continues to produce action potentials over the duration of the stimui. It conveys information about the duration of the stimulus. Tonic effects result from spending time on a task (vigilance).


Tonic Receptor Cells

Phasic receptors rapidly adapt to a stimulus. The response of the cell diminishes very quickly and then stops. It conveys information on rapid changes in stimulus intensity and rate. Phasic effects result from brain changes induced by warning signals or targets.


Phasic Receptor Cells

Based on the following scenario, identify the specific type of environmental information that the auditory sensory receptors are specialized to detect, and explain the fundamental role these receptors play in the process of hearing.

Sensory Receptor Specialization

Sensory receptors are specialized neurons that are uniquely responsive to specific types of stimuli from the environment. Their function is to detect sensory information, such as light, sound, or pressure, and initiate the process of sensation.

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Sensory receptor organs act as filters of the environment by responding to certain stimuli (ie. eyes for vision, ears for hearing). These organs, often times body parts, are particularly sensitive to some forms of energy.
- Receptor cells
- Hierarchy of Sensory Systems

Sensory Organs

Sensation is the initial process in which specialized neurons, called sensory receptors, detect environmental stimuli. This detection of sensory input provides the foundational data that the nervous system uses to understand the surrounding world.

Sensation

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

In most sensory systems, cells at all levels of the nervous system - from the surface sheet of receptors to the cerebral cortex - are arranged in an orderly, map-like manner. With bilateral receptor systems - the two ears or the two nostrils for example - the relative time of arrival of the stimulus at the two receptors is directly related to the stimulus.  

Hierarchy of Sensory Systems

Sensory Receptors

The common idea that humans have only five senses is oversimplified. Along with vision, hearing or audition, smell or olfaction, taste or gustation, and touch or somatosensation, humans also have sensory systems for balance, body position and movement, pain, and temperature.

The Senses

Refers to the conversion of sensory stimulus energy into action potentials by sensory receptors, enabling the communication of sensory information to the central nervous system.

A key example of sensation occurs in vision. When light enters the eye, it acts as a stimulus, causing chemical changes in the sensory receptor cells lining the back of the eye. These cells then relay this information to the central nervous system by generating messages in the form of action potentials.

Example of Sensation: Vision

Imagine you are walking barefoot on a beach. You step on a sharp seashell, and your foot immediately pulls back. Which of the following statements describes only the process of *sensation* in this experience?

Perception is the complex psychological process of organizing, interpreting, and consciously experiencing sensory information. It involves making sense of the raw data detected by sensory receptors, actively shaping our conscious experience based on focused attention, past experiences, and cultural background.

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