Human Neuropsychology Midterm 2 2026

Geniculostriate Pathway

The primary neural circuit responsible for conscious visual perception.

Carries visual information from the retina to the primary visual cortex (V1).

From VI, information splits into the dorsal stream and the ventral stream.

Tectopulvinar System

Secondary visual pathway in the brain that processes rapid spatial information and directs eye and head movements toward peripheral stimuli.

Multi-sensory integration (combines visual info with other sensory inputs to guide actions.

Blindsight (supports residual visual detection and localization in individuals with primary visual cortex (V1) damage.

Pathway of Geniculostriate System (Newer Pathway) vs Tectopulvinar System (Older Pathway)

G: Visual stimuli is presented to the Retina and receives input from all parvocellular (P-cells) and a portion of magnocellular (M-cells) retinal ganglion cells and is sent to the Lateral Geniculate Nucleus (LGN) of the Thalamus which send the stimuli to the Primary Visual Cortex (V1) in the Occipital Lobe.

T: The Retina receives predominately magnocellular retinal ganglion cells (~10% of retinal ganglion cells) and it is sent to the Superior Colliculus (in midbrain texture) to the Lateral Posterior-Pulvinar Complex of Thalamus and then the Extrastriate/Prestriate cortex (bypassing V1) as well as Parietal and Temporal Lobes

Functional Difference Between Geniculostriate and Tectopulvinar

G is responsible for conscious visual perception while T is responsible for unconscious responses to visual stimuli and reflexive vision.

G is involved in detailed pattern, colour, fine shape, and motion recognition, and T is involved in spatial attention in the peripheral vision and directs rapid eye movements and head turns.

G is split into the Ventral Stream for recognition and the Dorsal Stream for spatial awareness and T. Provides information on the absolute spatial location of objects.

T supports residual visual capacities (motion or spatial localization) in patients with damaged V1.

Ventral Stream

In the Temporal Lobe and is involved in the “what” and for object/face recogntion

Scene-based frame of reference

Relational metrics

Long-term representations

Conscious

Dorsal Stream

In the Parietal Lobe and is the “where/how” for spatial awareness.

Visual control of motor output

Effector-based frames of reference

Absolute Metrics

Moment-to-moment computations

Automatic

Visual Streams (V1 and V2)

V1: Visual processing starts here and projects to all major visual areas

V2: The secondary processing location, and it also projects onward to major visual areas.

The Ebbinghaus Illusion: Perceptually Different, Physically Identical

An optical illusion where two central circles of identical physical size appear to be different because of the context of the shapes surrounding them.

Dorsal Stream = Action - Doing the task - leads to grasps size appropriate for the middle circle

Ventral Stream = Perception - Estimating how to do the task - Leads to grasps size appropriate size NOT appropriate for the middle circle

Grasping after a delay is controlled by Ventral stream processes.

Theory of Occipital Lobe Function: V1, V2, V3, V4, V5

V1 and V2 - heterogenous general areas that process all types of visual information

Higher Visual Areas (more specialized):

-V3: Dynamic form/Shapes of the objects in motion

-V4: Colour Information Processing

-V5: Motion Processing

Damage to V1 can lead to blindness but some limited vision due to the higher visual areas still working. V1 seems to deal with AWARENESS of visual objects.

What did resting-state fMRI suggest about the Ventral Pathway?

The ventral pathway contains two parts: The lateral surface and the ventral surface of the temporal lobe

Visual Processing Hierarchy

There needs too be both objective recognition (ventral stream) and action (dorsal stream).

Which Visual Field has a bias to viewing faces?

The left visual field

Visual Space: Egocentric, Allocentric, Movements

Objects are described in terms of their relation to either the observer (Egocentric) or to another object (Allocentric).

Both are needed in order to guide movements and remember a visual scene!

What is the primary function of vision?

To guide movement

Which stream provides real-time visual control of action?

The Dorsal Stream

Role of Dorsal-Stream Neurons

Posterior Parietal visual neurons are active when the brain is ACTING on Visual Information. They provide a connection between the visual world that is perceived and the intent to take action in the world.

Imaging Studies of Dorsal and Ventral Streams

Comparing two faces:

-Activity in temporal love when asked to compare different faces

-Activity showed in parietal lobe when asked to focus on a specific part on one person’s face.

Asked to detect motion: V5 increased activity

Asked to detect colour: V4 increased activity

Disorders of Visual Pathways

Damage to visual cortex typically spares information from the central part of the visual field (macular sparing)

Scotomas: small blind spots that are often unnoticed because the eyes are constantly moving and the brain fills in the blind spots with information from previous position of the eyes.

Different Lesions in Area V1

Hemianopia: Right visual field gone

Quadrantanopia: Smaller injury = only part of a quadrant knocked out (right)

Scotoma: Even smaller injury = very small part of FOV in a quadrant knocked out (right)

Who is BK and why are they significant?

BK had V1 Damage and Scotoma

Primary vision damage and blindness in a small area.

Loss vision in LVF

MRI showed evidence of stroke in the right occipital lobe

Who is DB and why are they important?

V1 Damage and Blindsight

Removed part of right calcarine fissure (central focus of V1)

See nothing in LVF but feels something is there and guesses right

Cortical Blindness

Who is BI and why are they important?

Child with damage to the occipital lobe bilaterally in the first 2 weeks of life due to a genetic disorder

At 6 they are not blind

Significant plasticity to rearrange his visual system and strengthen pathways from subcortical areas to V5

Who is JI and why are they significant?

V4 Damage and Loss of Colour Vision