Temporal Lobes

Anatomy

All the tissue below the Sylvain fissure and anterior to the occipital cortex

Subcortical temporal lobe structures

• Limbic cortex

• Amygdala

• Hippocampal formation

Lateral surface

• Auditory areas (Brodmann’s areas 41, 42, 22)

• Ventral stream of visual information

  • Inferotemporal cortex (Brodmann’s areas 20, 37, 38)

Superior temporal sulcus (STS)

• separates superior and middle temporal gyri

• Receives input from auditory, visual, and somotatosensory regions

Medial temporal region (Limbic cortex)

Includes the amygdala, hippocampus, fusiform gyrus

Temporal Parietal Junction (TPJ)

• lying along the boundary of the temporal and parietal lobes

• At the end of the Sylvain fissure, including portions of the supramarginal and angular gyri

• Overlap with Wernicke’s area

Temporal lobe connections

• afferent projections from sensory systems

• Efferent projections to the parietal and frontal regions, Limbic system and basal ganglia

Which areas are connected via corpus callosum

left and right temporal lobes

which areas are connected via anterior commissure

Media temporal cortex and amygdala

5 cortico-cortical connections

1. Hierarchical sensory pathway

2. Dorsal auditory pathway

3. Polymodal pathway

4. Medial temporal projection

5. Frontal lobe projection

Hierarchical Ventral Sensory Pathway

• incoming auditory and visual information

• Stimulus recognition

• Primary and secondary auditory and visual areas to temporal pole

• Ventral visual and auditory projections form parallel streams

6 cortical and subcortical pathways comprise the stream

1. Occipitotemporal pathway to caudate nucleus and putamen

2. Inferotemporal cortex to amygdala

3. Inferotemporal cortex to ventral striatum

4. Medial temporal pathway

5. Orbitofrontal pathway

6. Ventrolateral prefrontal pathway

dorsal auditory pathway

• from auditory cortex to posterior parietal cortex

• Detection of spatial location/movement of auditory inputs

• Analogous to dorsal visual stream

Polymodal pathway

• series of parallel projections from auditory and visual association areas converge into Polymodal regions of STS

• Underlies stimulus categorization

Medial temporal projection

• Connections from auditory and visual association areas to medial temporal and Limbic regions

• Crucial to long term memory

• Perirhinal cortex to entorhinal cortex to hippocampal formation and amygdala

Frontal lobe projection

• series of parallel projections from temporal association areas to frontal lobe

• Necessary for aspects of movement control, short term memory and affect

temporal lobe functions

• sensory processes

• Affective responses

• Spatial navigation

Sensory processes

• identification and categorization of stimuli

• Developing object categories crucial to perception and memory; depend of inferotemporal cortex

• Memory

Affective responses

• emotional response is associated with a particular stimulus

• Animals with no amygdala lose fear

Spatial navigation

involves hippocampus; contains cells that code for spatial location

Tanaka and colleagues

• cells in inferotemporal cortex require complex features for activation (eg. Colour, size, texture)

• Specificity of neurons is altered by experience

Biological motion

• movements relevant to a species

• Allows us to guess others intentions

• Allows us to develop hypotheses about people

David Perrett and colleagues

• STS cells are maximally responsive to particular types of biological motion

  • Direction of eye gaze

  • Head movement and facial expression

  • Mouth movement (vocalizations)

Speech perception

• normal speech 8-10 segments per second, but we can perceive 30 segments per second

• Special mechanism is in the left temporal cortex

Music perception

Right temporal lobe extracts pitch from sound regardless if the sound is speech or music

Schneider and colleagues

• musicians have a larger volume of gray matter in Heschl’s gyrus (primary auditory cortex) in both temporal lobes

• Fundamental pitch listeners exhibit leftward symmetry

Left temporal lobe asymmetry

• verbal memory

• Speech processing

Right temporal lobe asymmetry

• nonverbal memory

• Musical processing

• Facial processing

Disorders of visual processing

• temporal lobe damage often impair object and pattern recognition

• Right temporal lobe lesions lead to abnormal face and biological motion perception

Cortical Deafness

• bilateral damage to auditory cortex

• Absence of neural activity in auditory regions

Wernicke’s Aphasia

• left temporal lobe

• Disturbed recognition of words

Disorders of music perception

• left posterior superior temporal gyrus damage affects rhythm discrimination

• Temporal regularity/beat discrimination affected by anterior damage to the right temporal lobe

Impaired categorization

left temporal lobe tommies and lesions lead to impairment in the ability to categorize words/pictures of objects

McGill Picture Anomalies Test

• visual scene is presented to the patient and asked what is out of place

• Right temporal lobe damage impairs this task

Anterograde Amnesia

Amnesia for events after bilateral removal of the medial temporal lobes

Inferotemporal cortex damage

Interferes with conscious recall of information

Left temporal lobe lesions

Impaired recall of verbal memory

Right temporal lobe lesions

Impaired recall of nonverbal material

Temporal lobe personality

• Right temporal lobectomy

• overemphasizes trivia and petty details of life

• Egocentricity

• Paranoia

• Prone to aggression

Speech perception

• sounds come from 3 restricted ranges of frequencies (formants)

• Sounds vary from one context to another yet all are perceived as the same

Music perception

• relies of relation between elements rather than individual elements

• Contains loudness, timbre, pitch

• Musical training induces plasticity

• Musicians have more gray matter in Broca’s area