Comparative Behavior Lecture 9

What is the focus of neuroscience in the study of behavior?

A mechanistic understanding of the proximate control of behavior

What does the adaptive function of behavior refer to?

How evolutionary (ultimate) mechanisms have shaped behavior

What is ethology concerned with?

Understanding how animals behave in their natural environments, often focusing on the evolutionary function of behaviors

How do bats use echolocation?

Bats send out high-frequency calls and listen to their echoes, using the timing and direction of echoes to locate objects in space

What problem do bats face when detecting echoes?

Spherical spreading losses, especially at high frequencies, make echoes weaker and harder to detect

What is required for bats to detect echoes effectively?

They need acute hearing at the right frequencies

What is the place theory of hearing?

The ability to sense frequency depends on different sound frequencies selectively vibrating different areas of the cochlea

How does the structure of the basilar membrane contribute to frequency detection?

Its thickness varies along its length, allowing different parts to resonate with different frequencies

How does the nervous system determine sound frequency?

Hair cells along the basilar membrane fire when they vibrate, so the nervous system identifies frequency based on which cells are activated

Why is the moustached bat’s tuning frequency shifted upward from its call frequency?

To match the frequency of returning echoes due to the Doppler effect, optimizing echolocation

What is an auditory fovea?

A region of the cochlea where frequency changes with place most slowly, allowing finer resolution for important frequencies like echoes

How is the bat’s cochlea specialized for detecting insect echoes?

It devotes more space to the frequency most relevant for detecting prey, enhancing sensitivity

How do bats maximize echo detection?

Through tuning of the audiogram, tuning of the acoustic fovea, and echo-detecting neurons that are specialized for this task

What did Griffin and Galambos discover about bats?

That bats use echolocation to find and catch insect prey

What did Kenneth Roeder suggest about nocturnal insects?

That they face strong selection pressure to detect bat echolocation signals and avoid predation

Do moths have ears adapted for detecting bat signals?

Yes, moths have simple ears with two auditory receptors (A1 and A2) linked to a tympanum that vibrates in response to sound

How many sensory neurons are in the moth ear and what do they do?

Two sensory neurons (A1 and A2) relay information to interneurons in the thoracic ganglia, which connect to motor neurons that control wing movement

How do A1 and A2 auditory receptors differ in function?

A1 receptors fire faster with increasing sound intensity, while A2 receptors fire only at high sound intensity

How do moths use auditory information to locate bats?

They compare signals between left and right ears to determine direction and turn away from the bat

Why do moths have an advantage in bat detection?

They can detect bats from \~30 meters away and turn to escape, while bats can only detect moth-sized prey from \~10 meters or less

What is categorical perception?

A phenomenon where animals perceive a continuous range of stimuli as discrete categories to focus on biologically meaningful differences

What are some human examples of categorical perception?

Speech sounds like

What did Marler and Pickert find in swamp sparrows?

They described six “species universal” note types in their song repertoires

What did Nelson and Marler discover about swamp sparrows?

They showed swamp sparrows perceive note types in a categorical fashion with a proposed perceptual boundary at 13 ms

How was categorical perception tested in swamp sparrows?

By habituating birds to a repeated note and then replacing it with a slightly longer note; birds became aggressive again if the note crossed the category boundary

What did physiological recordings from HVCX cells in swamp sparrows show?

They responded categorically to note types, with consistent boundaries across cells and birds

How did the neural CP boundary differ from Nelson and Marler’s behavioral boundary?

The neural boundary was found in a different population, suggesting variation in categorical perception between regions

What does the difference in CP boundaries across populations suggest?

That learned differences in note category boundaries function like dialects, influenced by cultural variation

What did studies in Pennsylvania swamp sparrows reveal about categorical perception?

The physiological CP boundary matched the local behavioral response, confirming that CP varies across populations

What does this research illustrate about neuroethology?

It links brain responses to behavior and shows how neural mechanisms can reflect both evolutionary and learned influences on perception