Sensory System Interactions. Flashcards
What is sound localisation important for? And how does this mechanism help is a noisy environment?
important for communication. And localising where people are in specific locations.
We use this mechanism to focus on one thing in a noisy environment
The older you are the harder it is to do sound localisation
How does sound localisation allow for perception of auditory space?
Enables perception of auditory space
This happens from taking information from the environment by the both ears
Sound is used to create an auditory map (remember the eyes make a visual map)
What is binaural hearing?
Binaural hearing?
Is when you hear sounds with both ears.
This helps you to located where a sound is i.e if its up or down
This also helps you to PREDICT where a sound will move next.
What is monaural hearing?
This is when you only hear with one ear
You can hear all the sounds but you can’t bin point where its coming from
Sound localisation (detecting where in space a sound is)
How to recognise sounds in the vertical plane (this is the plane of detecting and localising sounds from ABOVE or BELOW )?
What are spectral notches?
What causes them?
We use monaural cues (which require only one input from one ear)
The brain can detect events such as spectral notches (specific points detected by sound vibration) which are precisely timed to the onset of sound hitting the ear.
These are caused by sound bouncing off of the pinna which is the fleshy part of the outer ear.
Different features of the outer ear responsible for helping vertical plane detection?
Every fold of the ear interacts with sound in a different way and distorts this sound
This distortion creates a specific pattern (which can be transferred by neurones)
NOTE Different sounds note are TRANSFORMED in different ways
This helps us to tell the elevation of sounds and where sounds are coming from in the ventral plane.
What can analysing the different patterns caused by sound distortion of the outer ear help us to do?
Helps us to recognise sounds from past experiences. Also helps us to tell where a sound is coming from in the vertical axis
How does the different shapes of the ears between individuals affect spectral notches
Causes spectral notches (certain points detected in the sound distortions which have to be learnt) to differ in person to person
What is the experiment which shows we have adaptive learning processes?
An ear has an insert placed into it
This modifies the direction of the transfer function (how sound is absorbed and processed)
This means the individual cannot recognise where the sound is coming from.
WHAT HAPPENS WHEN THE INSERT IS LEFT?
If the inserts are left in for a long time the individual can RELEARN transfer function and then go onto localising it (saying where the sound is coming from)
Thus this suggests we have adaptive learning. We can correct misaligned sensory input.
What helps us to detect and localise sound in the horizontal plane (as in left or right)?
We use two binaural cues:
Interaural level differences
And interaural timing differences
What are Interaural level differences?
The brain compares LOUDNESS and INTENSITY of sounds arriving at two different ears.
This means that is something is closer to one ear than the other then that sound is louder at the ear the sound is closest to.
The head physically defects sound so its quieter at the other ear.
Sounds as small as 1 -2 dN can be detected
The degree of detecting the difference in sound loudness corresponds on how far / close the sound is to the centre line of the body
This detects sounds at HIGH frequencies
What are interaural timing differences?
The brain compares the difference in the arrival of time of sound at both ears. This is as small as 10 micro sec
Sounds closer to one early than the other reach the ear quicker thats its closest to
This is compared to the sound hitting the other ear
This detects sounds at lower frequencies
Sounds furthest away from the midline (centre of head) gives the longest time differences
What do most species use, interaural timing or level differences?
They use both
However one may dominate due to animals head size and hearing range
Auditory pathway. Where do all nerves from the cochlear go? Where is the cochlear nucleus? What are the two pathways in the auditory system?
All the nerves from the cochlear enter the cochlear nucleus
This is in the brain steam
Then the pathway from the brainsteam has two places
Information is either sent to cells for recognition or it is sent from the ventral cochlear nucleus (in briansteam) to other regions of the brainsteam responsible for localising sound.
What is the auditory pathway? Starting with the superior olivary complex?
Starts with the superior olivary complex in the brainstem. This is the circuitry for localising sounds in space is. Remember the ventral cochlear nucleus is in this brainstem too.
From here the pathway goes up to the inferior and superior colliculus
It then travels up to the medial geniculate nucleus (MGN) remember the lateral geniculate nucleus is form vision.
And then the auditory cortex (AC)