# Basal forebrain motivational salience signal enhances cortical processing and decision speed

## TL;DR

This paper reviews how a specific group of neurons in the basal forebrain helps animals quickly respond to important stimuli by enhancing brain processing.

## Contribution

The paper highlights novel insights into non-cholinergic basal forebrain neurons that encode motivational salience and modulate decision-making.

## Key findings

- Non-cholinergic basal forebrain neurons show ensemble bursting in response to behaviorally relevant stimuli.
- These neurons act as a gain modulation mechanism to enhance cortical processing and decision speed.
- This function is critical for behavioral flexibility and determining which stimuli require attention.

## Abstract

The basal forebrain (BF) contains major projections to the cerebral cortex, and plays a well-documented role in arousal, attention, decision-making, and in modulating cortical activity. BF neuronal degeneration is an early event in Alzheimer’s disease (AD) and dementias, and occurs in normal cognitive aging. While the BF is best known for its population of cortically projecting cholinergic neurons, the region is anatomically and neurochemically diverse, and also contains prominent populations of non-cholinergic projection neurons. In recent years, increasing attention has been dedicated to these non-cholinergic BF neurons in order to better understand how non-cholinergic BF circuits control cortical processing and behavioral performance. In this review, we focus on a unique population of putative non-cholinergic BF neurons that encodes the motivational salience of stimuli with a robust ensemble bursting response. We review recent studies that describe the specific physiological and functional characteristics of these BF salience-encoding neurons in behaving animals. These studies support the unifying hypothesis whereby BF salience-encoding neurons act as a gain modulation mechanism of the decision-making process to enhance cortical processing of behaviorally relevant stimuli, and thereby facilitate faster and more precise behavioral responses. This function of BF salience-encoding neurons represents a critical component in determining which incoming stimuli warrant an animal’s attention, and is therefore a fundamental and early requirement of behavioral flexibility.