Chapter 6: Object Recognition

What is object recognition?

The process of perceiving a coherent, meaningful object from visual input.

What is object constancy?

The ability to recognize objects despite changes in size, orientation, or lighting.

Why is object constancy important?

It allows stable perception in a constantly changing visual environment.

What are the two main visual pathways?

The ventral (“what”) pathway and the dorsal (“where/how”) pathway.

What is the function of the ventral stream?

Object recognition, identifying what an object is, and visual memory.

What is the function of the dorsal stream?

Spatial perception and guiding actions toward objects.

Why is the dorsal stream sometimes called the “how” pathway?

Because it guides how we interact with objects, not just where they are.

Where does the ventral stream project to?

The temporal lobe.

Where does the dorsal stream project to?

The parietal lobe.

What happens with temporal lobe (ventral) damage in monkeys?

Impaired object discrimination.

What happens with parietal lobe (dorsal) damage in monkeys?

Impaired spatial/landmark discrimination.

What is a key difference in receptive fields between ventral and dorsal neurons?

Ventral neurons are foveal-focused, dorsal neurons often respond to peripheral vision.

What is object constancy supported by?

The ventral stream.

How does complexity of stimuli change in the ventral stream?

Neurons respond to increasingly complex stimuli moving anteriorly.

What is the main role of dorsal stream neurons?

Detecting presence and location of stimuli and guiding actions.

Who is patient D.F.?

A patient with ventral stream damage who cannot recognize objects but can guide actions.

What deficit does patient D.F. have?

Inability to recognize objects based on shape.

What ability does patient D.F. retain?

Ability to correctly perform actions toward objects.

What is an explicit matching task?

A task requiring object recognition (ventral stream).

What is an action (visuomotor) task?

A task requiring physical interaction with objects (dorsal stream).

What is optic ataxia?

A disorder where patients can recognize objects but cannot use vision to guide actions.

What is visual agnosia?

A visual perception disorder where patients cannot recognize objects.

What does optic ataxia indicate about brain function?

Dorsal stream is critical for action guidance.

What does visual agnosia indicate about brain function?

Ventral stream is critical for object recognition.

How do the dorsal and ventral streams interact?

They are independent but interconnected and work together for perception.

Why is interaction between streams important?

To bind object identity with location.

What is TMS?

Transcranial Magnetic Stimulation, a method used as a virtual lesion to study brain function.

What is ensemble coding?

Object recognition through collective activation of many neurons.

Why is ensemble coding useful?

It allows recognition even if some neurons fail.

What does ensemble coding explain about perception?

Why we recognize similarities and sometimes confuse objects.

Are neurons perfectly selective for one object?

No, neuron selectivity is not absolute.

What are face patches?

Clusters of neurons that respond strongly to faces.

How were face-selective neurons discovered?

Using fMRI and single-cell recordings in monkeys.

What is the fusiform face area (FFA)?

A region in the fusiform gyrus specialized for face recognition.

Where is the FFA located?

On the ventral surface of the temporal lobe.

What does the FFA respond strongly to?

Faces more than other objects.

Is the FFA just for expertise in general?

No, it is specifically tuned for faces.

What evidence argues against FFA as general expertise?

Different activation patterns for non-face expert categories.

Why might faces have specialized processing?

They require fine perceptual discrimination among similar stimuli.

What is configural processing?

Processing based on overall shape and spatial relationships between features.

Why is configural processing important for faces?

Because facial recognition depends on spatial arrangement of features.

What other categories show brain selectivity?

Bodies and scenes.

Why might category-specific processing exist?

Due to evolutionary importance for survival.

What is the main goal of object recognition?

To identify and interpret visual objects accurately.

What does the ventral stream primarily answer?

“What is it?”

What does the dorsal stream primarily answer?

“Where is it?” or “How do I interact with it?”

What is required to fully recognize an object?

Integration of identity (ventral) and location (dorsal).