Temporal Lobe

Detailed Treatment

Connections of the Temporal Lobes

• Five main types:– Hierarchical sensory pathway– Dorsal auditory pathway– Polymodal pathway– Medial (mesial) temporal pathway– Frontal lobe projection

Connections of the Temporal Cortex

• Hierarchical sensory pathway– Connections from primary (sensory neuron) and secondary (integration

functions; additional neurons connected to the primary neurons) auditory and visual cortical regions progress through the lateral temporal cortex and terminate in the temporal pole (anterior end of the temporal lobe)

– Connections in the temporal pole are then relayed to the medial aspects of the temporal lobe• Visual travels through the area corresponding to the inferior temporal gyrus• Auditory travels through the area corresponding to the superior temporal gyrus

(STG)• Major destinations:

– Amygdala and hippocampus– This results in the integration of information into: memory, retrieval of stored information,

emotional tone

• Ultimate Effect: stimulus recognition– The familiar conscious experience of knowing, assimilating, and feeling

Hierarchical sensory pathway

Sound entering each ear is processed by the contralateral hemisphere

Connections of the Temporal Cortex

• Dorsal auditory pathway– Forms important

functional connections with the posterior parietal cortex

– Enables location of sounds in space

– Promotes orienting and initiation of movements relative to sound location

Connections of the Temporal Cortex

• Polymodal Pathway– Connections emerging from the auditory and

visual hierarchical pathways– Directed towards the neurons enfolded within the

superior temporal sulcus– Polymodal nature of neurons• Believed to be involved in assigning stimuli to

categorical classes, linked to and can be retrieved by memory

Polymodal pathway

Connections of the Temporal Cortex

• Medial Temporal Projection– Projections from auditory and visual areas into the

limbic regions• E.g., amygdala and hippocampus

– Directions of projections• Peripheral cortex → entorhinal cortex →

amygdala/hippocampus• Perforant pathway forms the main projection to the

hippocampus• Damage in this region severely affects memory formation

Insular Cortex

Connections of the Temporal Cortex

• Frontal-lobe Projection– Neurons from the temporal lobe have strong

connections with the frontal lobe– Posterior temporal cortex• Projects to the dorsolateral prefrontal cortex (top

arrow)

– Anterior temporal cortex• Projects to the orbital frontal cortex• Damage leads to terrible life decisions

Temporal Lobes

Effects of Damage

Summary of Major Symptoms

• Impaired auditory sensation• Impaired selection of visual and auditory input• Impaired visual and auditory perception• Disordered perception of music• Impaired ability to organize and categorize information• Poor use of contextual information• Impaired language comprehension• Impairment in long-term memory• Changes in personality and affect

Auditory Perception

• Paradoxically, unlike the perceptual effects of spontaneous neural activity in the auditory cortex (i.e. one experiences auditory sensations), bilateral damage to the primary cortex does not lead to cortical deafness– Contrast with damage to primary somatosensory

or visual cortex

Auditory Cortex

• Discriminates two forms of auditory processing– Rapidly presented stimuli• E.g., rapid presentation of language needs to be quickly

analyzed

– Complex patterns of stimuli• E.g., music has slower changes in frequency

Speech perception

• Patients with left temporal lobe damage have difficulty discriminating sounds

• Complain that people are talking too fast– In reality, there is an impairment in discriminating

between rapidly delivered sound units inherent in speech• Problems in judging the temporal sequence of heard

sounds– Normally, two sounds resolved within 50-60ms– Damage results in 10-fold increase in temporal

requirement for discrimination (i.e. about 500ms)

Summary of areas activated by different sound stimuli

Schizophrenia

• Disorder of thought and emotion• Not “split-personality”• Indicence: approx. 1%– No gender differences

5 Symptom Dimensions of Schizophrenia