Temporal Lobe

Side of the head

Data is crawling across the side of your head.

The temporal lobe is critical for processing vision, memory and sound. We’ll look at all three. For vision, there are two streams of visual information come from the occipital lobe. First, we’ll look at the info sent to the temporal lobe.

Auditory information comes from the eyes, passes through the inferior colliculus, then the MGN, and finally reaches the superior region of the temporal lobe. As it passes through the temporal lobe, sound info is processed with increasing complexity, and shared with the parietal and frontal lobes. The auditory cortex is structured concentrically, with the primary cortex in the middle.

Temporal Lobe
- Ventral = high level visual process
- Medial = memory
- Superior = cochlea
- Posterior = audio-motor proces
- Temporal-parietal = Wernicke
I. Ventral area of temporal lobe
- ventral = toward the tummy; under part of temporal lobe
- Ventral Stream
  - Occipital to temporal
  - Under part of temporal lobe
  - Main input from LGN
  - Parvocellular cells of V4
- As info moves thru temporal lobe
  - Processes larger receptive fields
  - Takes longer to process
  - Analyses more complex
- Representation of entire visual field
  - Uses cues to judge significance
  - Attention
  - Stimulus salience
  - Working memory
  - High-level visual processing
  - Complex stimuli
  - Faces (fusiform gyrus)
  - Scenes (parahippocampal)
  - Surrounds hippocampus
- Inferior temporal gyrus
  - Visual processing
  - Complex object features
    - global shape
    - face perception?
  - Fusiform gyrus = faces
  - Parahippocampal = scenes
  - Lingual gyrus
    - Word recognition
    - Dreaming
II. Medial Temporal Lobe
- Medial = toward median; toward middle
  - Declarative memory
  - Facts you know – L hemisphere
  - Events you’ve experienced – R
- Interacts with frontal lobes
  - Create long-term memories
  - Maintain long-term memories
  - Long-term memory
    - Becomes independent of encoding process
  - Hippocampus & adjacent areas work together
    - No simple dichotomies
    - associative vs. nonassociative
    - episodic vs. semantic memory
    - recollection vs. familiarity
- Transfer from STM to LTM
- Control spatial memory
- Damage causes
  - anterograde amnesia
- Declarative (explicit) memory
  - Semantic memory
    - Left hemisphere
    - Facts
  - Episodic memory
    - Right hemisphere
    - What I did on my vacation
III. Superior Temporal Lobe
- superior = upper
- Cochlea to auditory cortex
A. Primary auditory cortex = sound
- Anatomy of the Ear
- 1. Outer Ear
- 2. Middle Ear
- 3. Inner Ear
1. Outer Ear = pinna
- Pinna (pinnae) – visible ear
  - funnels sound to ear drum
  - helps in sound localization
- Tympanic membrane
  - Connects pinna to ear drum
  - Vibrates to sound wave
- Eustachian tube = equalizes pressure
2. Middle Ear
- Ossicular Chain
  - Pre-amplifier
    - amplifies vibrations 20x
    - 3 small bones
  - Malleus
  - Incus
  - Stapes
- Attenuation reflex
  - brain senses loud sound
  - tenses up muscles
  - To prevent damage
    - Bones don’t move
    - Greater for low frequencies
      - (higher freq. easier to discern)
3. Inner Ear
- A fluid-filled structure
  - fluid is called endolymph
  - similar to intracellular fluid
  - high in potassium
  - low in sodium
- Composed of
  - Bony labyrinth
  - Membranous labyrinth
    - suspended within bony labyrinth
    - delicate continuous membrane
  - Space between membranous & bony labyrinths
  - Filled with perilymph, similar to cerebral spinal fluid
2 outlets to air-filled middle ear
- Oval window
  - Filled by plate of stapes
  - Fluid pressure
- Round window
  - Pressure valve
Cochlea
- Spiral-shaped tube
- Has 2 connected canals
- Upper vestibular canal
- Lower tympanic canal
- Separate at large end
  - continuous at the apex
- Fluid filled (perilymph)
  - Has a middle canal
  - Cochlear duct
  - Filled with endolymph
- Contains the Organ of Corti
Organ of Corti
- “spiral organ”
- Contains hair cells for hearing (cilia)
- Basilar membrane with hair cells rest on it
- The basilar membrane separates the cochlear duct from the tympanic canal
- The tectorial membrane lies above the hair cells
Stereocilia
- Connected by extracellular links
- Graded in height
- Arranged in bundles
- Pseudo-hexagonal symmetry
How cochlea works
- Contains fluid
- Moving fluid $ hair cells, signals sent to brain, perceived as sound
- Arranged from high to low notes
  - low notes travel farther
Hearing Loss
- Bad bone conduction
  - Hearing aids
- Bad cochlea
  - Implant
- Dead cilia
  - ?
Most common causes
- Age (presbycusis)
  - Gradual, steady loss
- Noise
  - Motorcycles, lawn mower
  - Music in headphones
  - Gun shots
- db
  - 0 barely audible
  - 20 leaves ruffling
  - 40 quiet suburbia
  - 60 speaking voice
  - 100 subway train
  - 140 jet taking off
- Obstructions
  - Earwax
  - Objects
- Chemicals
  - Some antibiotics
  - Arsenic, mercury, tin, lead
- Head injury
  - Structural damage
- Infections
  - Middle ear (otitis media)
  - Swimmer’s ear (otitis externa
  - Fluid (cold or flu)
Preventing Loss
- Good genes
- Cover your ears
  - Lawn movers
  - Guns
- Don’t smoke
  - Correlation, cause unknown
  - Oxygen
  - Neurotransmitters
  - Developing brain
- No loud music
Processing Sound
- Vestibulocochlear nerve
- Cochlea but stops at cochlear nuclei
Neural Path
- Cochlei
- Cochlear nuclei
- Superior olivary complex
- Inferior colliculus
- Thalamus (medial geniculate nuclie)
- Primary auditory cortex
Cochlear nucleus
- 1st processing
Dorsal cochlear nucleus
Ventral cochlear nucleus
Superior olivary complex
- In the pons
- Input: ventral cochlear nucleus
  - Lateral superior olive (LSO)
    - Detecting ineraural level
  - Medial superior olive (MSO)
    - Interaural time difference
Inferior colliculi
- Just below superior colliculi
- Visual processing centers
- Integrates sound source info
Medial geniculate nucleus
- Thalamic relay system
- The LGN of sound
Auditory Cortex
- Highly organized into 3 parts
- Concentrically with primary in the middle
  - Primary auditory cortex
  - Secondary auditory cortex
  - Tertiary auditory cortex
1. Primary Auditory
- Direct input from MGN
- Tonotopically organized
- Identifies loudness, pitch, rhythm
- Neurons are organized:
- Frequencies respond best to
- Low frequencies at one end
- Complete “frequency map”
- Tonotopic map
  - Maps for vision & hearing
    - Reina to cortex
    - Cochlea to cortex
2. Secondary Auditory
- Surrounds primary cortex
- Interconnect
- Further processing
- Process patterns of
- Harmony
- Melody
- Rhythm
3. Tertiary Auditory Cortex
- Integrates musical experience
What it all does
- Analyses
- Identifying auditory objects
- Segmenting streams
- Identifying location of a sound
- How it all works
- Unclear
Inputs
- Multiple sounds
- Occur simultaneously
Tasks
Which components go together
- location of sounds
- groupings based on
  - Harmony
  - Timing
  - Pitch
Connects to Frontal & Parietal lobes too
- Why each note played by different instrument in orchestra sounds different
- Same pitch
Gamma waves
- Ss exposed to three or four cycles of 40 hertz click
- Spike in EEG
- Hallucination 12-30 Hz
- Left auditory cortex of schiz.
When remember song in mind
- Don’t perceive sound
- Experience melody, rhythm & overall experience
B. Wernicke’s Area
- Where temporal & parietal lobes meet
- Understanding of written
- Understanding speech
- Auditory word recognition
- Mimicking words
- Dominant Side
  - Usually left hemisphere
  - Resolve associative meanings
  - Bank———teller
- Non-Dominant Side
  - Usually right hemisphere
  - Resolve subordinate meanings
  - Ambiguous word meaning
  - River bank
  - Money bank
- Damage to Wernicke’s Area
  - Receptive aphasia
  - Also called
    - Fluent aphasia
    - Jargon aphasia
  - Impairs language comprehend
  - Natural-sounding rhythm
  - Normal syntax
  - Gibberish
  - Nonverbal sound problems
  - Animal noises
  - Machine sounds

Data is crawling across the side of your head.

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