Receptive Fields and the Visual System

Retinal Ganglion Cells (RGCs)

Receive signals from photoreceptors via the bipolar cells and amacrine cells and send action potentials to the brain via the optic nerve

Retinal Bipolar Cells

transmit signals between photoreceptors and ganglion cells

Amacrine and Horizontal Cells

Receive input from photoreceptors and send signals laterally within the retina. May send inhibitory signals to adjacent photoreceptors, bipolar or ganglion cells.

Lateral Inhibition

Mediated by the amacrine and horizontal cells. In RGCs, firing rate is reduced when areas of the retina adjacent to the excitatory portion of its receptive field are stimulated due to this process.

Centre-Surround Antagonism

Common arrangement found in receptive fields where the neural response to light placed in the centre is opposite to that in the surround. Stimulation of the inhibitory surround/centre counteracts the centre/surrounds excitatory response, causing a decrease in the neurons firing rate.

Receptive Field

the region of the sensory surface that, when stimulated, causes a change in the firing rate of that neuron

Simple Cells

Neurons in the primary visual cortex (V1) that respond maximally to straight-edge stimuli in a certain position and orientation

Orientation Tuning Curve

determined by measuring the responses of a simple cortical cell to bars with different orientations

Complex Cells

Neurons in the visual cortex that respond best to bars with a particular orientation moving in a specific direction

End-Stopped Cells

Neurons in the visual cortex that respond best to corners or bars of a specific length that are moving in a particular direction.

On-Centre Cell

A cell that increases firing in response to an increase in light intensity in the centre of its receptive-field and decreases firing in response to light in the surround of its receptive field

Off-Centre Cell

A cell that increases firing in response to a decrease in light intensity in the centre of its receptive-field (or increases firing in response to an increase in light intensity in the surround of its receptive-field and decreases firing in response to light in the centre of its receptive field)

Optic Chiasm

Point at which the part of the optic nerve coming from the nasal retina in each eye decussates to the contralateral side of the brain.

Nasal Retina

Part of retina for each eye that is located close to the nose. Receives light incoming from temporal portion of the visual field.

Temporal Retina

Part of retina for each eye that is located close to the ears. Receives light incoming from nasal portion of the visual field.

Lateral Geniculate Nucleus (LGN)

A structure in the thalamus that receives input from the retinal ganglion cells and has input and output connections to the visual cortex. Left side receives input from right visual field and vice versa.

Hubel and Wiesel

Won a Nobel prize for their research on feature detectors in visual cortex - discovered simple, complex, and end-stopped (hypercomplex) cells

Hartline (1938)

Discovered and coined the term 'receptive field' by recording from ganglion cell axons in the optic nerve of a frog

Kuffler (1953)

Demonstrated the presence of centre-surround receptive fields in mammalian retinal ganglion cells by stimulating the retina of cats

Centre-Surround Receptive Fields

The organisation of receptive fields in RGCs and cells within the lateral geniculate nucleus

Retinotopic Map

Organisation in the LGN and primary visual cortex in which each cortical area corresponds with a specific area of the retina

Primary Visual Cortex

The region of the cerebral cortex in the posterior medial occipital lobe that receives visual information from the lateral geniculate nucleus. Also known as area V1.

Visual Association Cortex

Includes areas V2-5. Processes increasingly complex visual information provided by the feature detectors in area V1 allowing us to perceive colour, shape, objects and movement.

Dorsal Visual Stream

Pathway that originates in the occipital cortex and projects to the parietal cortex. Otherwise known as the 'where' pathway, it processes information that facilitates our perception of the location of objects and how action is to be guided toward objects.

Ventral Visual Stream

Pathway that originates in the occipital cortex and projects to the temporal cortex. Otherwise known as the "what" pathway, it processes information that facilitates our perception of form, structure and recognition allowing us to determine what an object is.

Striate Cortex

Another term for the primary visual cortex.

Extrastriate Cortex

Another term for the visual association cortex

Feature Detectors

neurons that respond selectively to very specific features of more complex stimuli (such as orientation, movement, colour, shape etc.)