An adequate stimulus is the type of stimulus for which a given sensory organ is particularly adapted. For example, the adequate stimulus for the eye is photic (light) energy. Furthermore, an electrical shock on the eye can create an illusory sensation of light.

Adequate Stimulus

Labeled lines is the concept that particular neurons are established at the outset for distinctive sensory experiences. For example, neural activity in one line signals a sound, whereas activity in another line signals a smell. The "lines" can become even more specific within modalities. 
This theory of stimulus type identification is correct, unlike the previous theory of specific nerve energies (check child nodes). 

Labeled Lines

Sensory organs and peripheral sensory pathways convey limited and, sometimes, distorted information to the brain. This is because a great deal of selection and analysis takes place along sensory pathways before conscious perception of the stimulus.
- Coding

Selection and Analysis Along Sensory Pathways

For the somatosensory and visual systems, cells are arranged in an orderly fashion, much like a map. This map reflects receptor position and density, and is not one-to-one exact (see somatosensory homunculus and higher foveal cortical representation). Densely innervated sites, like the fingers and lips, have higher cortical representation.
 
In bilateral receptor systems (two ears and two nostrils), localization is different. It is determined by general time of arrival at the two receptors, and/or stimulus intensity. For example, if a soundwave hits your left ear sooner than your right ear, the source of the sound is probably to your left. If this soundwave is loud, it’s probably close. 


Stimulus localization

The sensory systems of a particular animal are very selective. In other words, sensory organs in each organism are sensitive to a specific range of the stimuli the organ is specialized for.

Selectivity and Range of Response to Stimuli

A stimulus (plural: stimuli) is an event that affects the sensory organ. Stimuli can be sound waves, light entering the eye, or food touching the tongue.
- Adequate stimulus
- Labeled Lines
- Stimulus localization
- Selection and analysis along sensory pathways
- Selectivity and Range of Response to Stimuli

Johns Hopkins University

University of Rochester

Sensory receptors such as eyes or taste buds develop differently in different species. Sensory processing refers to the ways the brain integrates information received from sensory receptors in order to process appropriate behavioral or cognitive response. 

- Sensory organs
- Stimuli
- Receptor Cells
- Touch and the skin
- Pain
- Sensory processing disorder
- Synesthesia

Sensory processing, touch and pain

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

Behavioral Neuroscience 8th Edition

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

Stimuli

A condition in which a stimulus in one modality can trigger experiences in another or multiple other modalities. For example, to someone with this condition (a synesthete), the letter could be seen as green, or a particular musical tone could evoke a particular taste sensation. 
For the colored letters and numbers, some studies have pointed to this association with popular toys that depict these figures in the same colors. 

Synesthesia

A large part of our somatosensory system is responsible for our perception of touch.
- Sensory Organ: Skin
- Dorsal Column System
- Primary Sensory Cortex
- Secondary Sensory Cortex
- Skin sensory receptors

Somatosensory System: Touch

The somatosensory system is partly responsible for detecting painful stimuli. Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
- Importance of Pain
- Congenital Insensitivity to Pain
- Classifying Pain
- Biological Basis of Pain

Somatosensory System: Pain

Sensory processing, touch and pain references

A condition where the brain has trouble receiving and responding to sensory input. May affect one or multiple senses. Symptoms could include over-sensitivity to certain stimuli, difficulties with coordination, or failure to respond to outside stimuli. This disorder is often seen in individuals on the Autism spectrum. It is not currently recognized as a distinct medical diagnosis.

Learn Before

Related

Learn After