Knowledge Base

Definition

An event scored when the animal visits specific zones in:

• Alternations: Multiple entries into different zones, with no reentries, in overlapping sets of zone entries. For example, for a Y maze with three zones A, B and C, the sequence of zone entries ABC is an alternation.
• Revisits: Multiple entries into the same zone. They can be direct (for example, AA) or indirect (for example, ABA).

Consider the zone entry sequence in a Y-maze: ABCBACBCAB. The eight overlapping 3-zone entry sequences are: ABC, BCB, CBA, BAC, ACB, CBC, BCA, CAB. Of these, six are alternations (underlined): ABC, BCB, CBA, BAC, ACB, CBC, BCA, CAB.

Alternation is often calculated together with the maximum possible number of alternations for the given sequence (that is, the total number of zone entries minus 2). In this example, it is 10 - 2 = 8.

The sequence above results in zero direct revisits, and two indirect revisits: BCB and CBC.

How to Specify Zone Alternation

1. Click the Add button next to Zone alternation.
2. In the Zone Alternation tab, under Settings, choose the zones that define the alternation.
3. Under Threshold, enter the Zone exit threshold. That is, once the animal is detected in a zone, the animal is considered to be in the zone until its distance from the zone border exceeds that threshold. Use this option to remove false re-entries resulting from random movements of the body point around the zone border.
4. Under Calculate Statistics for, select the options you require:
   • Alternations: To calculate statistics of alternations (ABC, ACB, etc.).
   • Max alternations: To count the maximum possible alternations given the sequence of zone entries in your data.
   • Direct revisits: To calculate statistics of the direct revisits (AA, BB, etc.).
   • Indirect revisits: To calculate statistics of the indirect revisits (ABA, ACA, etc.).
5. Complete the procedure to add the variable. See Calculate Statistics: Procedure.

Applications

In a T-maze or Y-maze experiment, you can use Zone alternation to analyze Spontaneous Alternation. See Hughes (2004) Neuroscience & Biobehavioral Reviews, (5), 497–505.

• In the Zone alternation tab, select the arm zones. If the arm zones are separated by a Center zone in the same zone group, do not include the Center zone.
• Also select Max alternations. The ratio Alternations/Max alternations expressed in percentage gives the spontaneous alternation index. An alternation index around 50% indicates random arm selection.

Notes

• If your experiment is set to Center-point, nose-point and tail-base detection, click the Body points tab and select the body points you want to use for calculation. If you have chosen two or three body points, select one of the following from the list:
  • Each point: Alternations and revisits are scored for each point separately.
  • Any selected point: Alternations and revisits are scored no matter which selected point enters a zone.
  • All selected points: Alternations and revisits are scored when all the selected points are in a zone simultaneously.
• Max alternations measures the maximum number of alternations that are possible with the actual data and given that number of zones considered. It is calculated as follows:

  Max Alternation = Total visits - (Number of zones - 1)

  • Total visits is the total number of zone visits.
  • Number of zones is the number of zones chosen under Settings; for the Y maze this is 3, for the plus maze it is 4.

  For example, given a sequence of 22 visits to zones A, B, and C, Max alternations is 22 - (3 - 1) = 20. The number of visits is diminished by two to account for the fact that the last two visits in the sequence are not part of complete alternations, because the remaining visits are unknown. A value of 20 means that if the animal had visited each zone after visiting the other two in the previous two visits (ABCABC, etc.), it would have made 20 consecutive alternations (ABC, BCA, CAB). An example of this procedure can be found in Ragozzino and Gold (1994), Journal of Neuroscience (12), 7478–7485.

• In Integrated Visualization, a Max alternations event is scored from completion of the first set of entries and for each new zone entry from that point. In the Statistics results, the total number of those events is shown under Frequency.
• Direct revisits are evaluated in 2-zone entry sequences, ignoring entries in zones not selected in step 2. For example, the sequence ADA results in one direct revisit (AA) when D is not selected.
• Indirect revisits are evaluated in 3-zone entry sequences, ignoring entries in zones not selected in step 2. For example, the sequence ABDAB results in the indirect revisits ABA and BAB when D is not selected.
• Direct revisits and indirect revisits are calculated when you select at least two and three zones, respectively.

Source: EthoVision XT 19 Help, Noldus Information Technology