Description of the Barnes maze strategies called by the Rtrack classifier

Introduction

The Barnes maze classifier provided by this package assigns one of 9 strategies to each Barnes maze path. The strategies are described here together with some notes on their interpretation.

Non-goal-oriented strategies

These strategies are not driven by an attempt to find the goal. Typically they are motivated by a desire to escape the testing arena, or by anxious immobility. In the Barnes maze, there may also be limited motivation to solve the task if the lighting (intended to be mildly aversive) is insufficiently bright.

Strategy 1: Passive

Passivity is likely an anxiety-related behaviour and is characterised by extended periods of immobility, which may be beside a non-goal hole or entirely outside any hole vicinity.

Strategy 2: Chaotic

The subject wanders randomly along a path that is generally not associated with hole positions. This behaviour may be anxiety-related.

Strategy 3: Random

The subject visits holes throughout the arena and in no particular order, with no obvious attempt to search for a goal (or even awareness that a goal exists).

 

Procedural strategies

These strategies involve the use of egocentric behaviours, where the search context is relative to the subject itself. As there are limited goal positions, the Barnes maze can, in fact, be solved in reasonable time using a procedural strategy. On balance, this will be much less efficient than a goal-directed strategy however. This behaviour is often observed following reversal, where the new goal position is unknown. Serial search would seem to be a reasonable strategy in such cases—but should be replaced by directed searches in later trials.

Strategy 4: serial

Holes are investigated one after the other in a constant direction. It can be difficult to distinguish from goal-directed searches in some cases as the subject may encounter the goal by chance after having visited only a few incorrect holes.

 

Allocentric search strategies

These strategies require the subject to orient itself using distal cues that are in the same frame of reference as the goal. Once a cognitive representation of the distal environment (a ‘spatial map’) has been constructed, a direct path to the goal can be rapidly calculated. A spatial map also allows a change in goal position to be quickly re-learned.

Strategy 5: Erratic search

This category describes an ultimately successful goal-directed search but where major errors (such as investigation of 1 or 2 holes outside the goal region) have occurred. Despite the initial disorientation, this pattern ends with a clearly goal-directed path.

Strategy 6: Goal-directed search

The subject moves in a goal-oriented manner, but not necessarily always correctly. There may be orientation loops, path corrections and path retracing for re-orientation employed. The search may begin at holes adjacent to the goal.

Strategy 7: Corrected search

The subject moves in an almost direct path to the goal, but makes one or two mistakes, which are corrected by reorientation. Errors can be a small loop to quickly scan the environment to allow re-orientation (‘orientation loop’), a course change (‘path correction’) or a larger loop where the subject returns to a previous point in the path and attempts the search again (‘re-orientation bight’). A brief investigation of one hole directly adjacent to the goal may occur.

Strategy 8: Direct path

The subject moves in a direct line to the goal.

Strategy 9: Perseverance

The search pattern involves an initial goal-directed search towards the previous goal location. This strategy is only called when an old goal position is defined. In the case of a goal position change, this strategy is termed ‘perseverance’. The nature of the Barnes maze means that lack of an escape box is easily and rapidly determined so that repeated investigation is not necessary. There may be brief investigation of neighbouring holes, but otherwise the subject will likely switch immediately to an alternative search strategy (see note in Procedural strategies above).