Rapid Effects of Selection on Brain-wide Activity and Behavior

Area of Science:

• Neuroscience
• Evolutionary Biology
• Behavioral Genetics

Background:

• Interindividual variation in behavior and brain activity is a universal substrate for natural selection.
• Selective pressures can alter behavioral traits at the population level, but underlying neural changes are often unclear.
• Endocrine and neuromodulatory systems are implicated in behavioral diversity and evolutionary adaptation.

Purpose of the Study:

• To investigate brain-wide activity patterns in zebrafish selectively bred for extreme differences in acoustic startle response (ASR) habituation.
• To identify neural circuitry changes associated with rapid evolutionary adaptation of a defensive behavior.

Main Methods:

• Selective breeding of larval zebrafish over two generations for high and low ASR habituation.
• Analysis of brain-wide activity patterns using functional imaging.
• Investigating the role of dopaminergic tyrosine hydroxylase (TH) neurons and caudal hypothalamus (HC) neurons.
• Assessing adult stress responses and other behavioral traits.

Main Results:

• High ASR habituation selection increased sound-evoked activation in ASR-processing areas.
• Low ASR habituation selection increased spontaneous activity in ASR-processing centers.
• Dopaminergic TH neuron ablation reduced ASR sensitivity; HC neurons linked to habituation lineages.
• High habituation correlated with decreased spontaneous swimming and altered adult stress responses.

Conclusions:

• Rapid selective pressure on ASR habituation induces significant brain activity differences.
• Evolutionary selection can rapidly modify neural circuits underlying behavior.
• Associated behavioral traits may be co-selected, impacting overall fitness.