Learning two conflicting motor tasks is associated with anterograde interference but also with facilitation in a time-dependent manner

PEDRO ALEJANDRO CAFFARO; JORGE IGNACIO VILLALTA; VALERIA DELLA MAGGIORE

Rio de Janeiro

Congreso; IBRO - 9th World Congress International Brain Research Organization; 2015

International Brain Research Organization

Although abundant evidence points to the formation of long-term motor memories several previous studies have failed at characterizing the time course of memory consolidation using behavioral protocols of retrograde interference (e.g. Bock and others, 2001; Goedert and Willingham, 2002; Caithness and others, 2004). This may in part be due to the fact that anterograde effects are very strong, often masking retrograde effects of interest at recall (Miall et. al., 2004). Here, we took advantage of this phenomenon to explore the time course of motor memory consolidation based on anterograde interference.Subjects performed two opposite visuomotor tasks following a protocol of anterograde interference. Participants were divided into 6 groups, which experienced a clockwise rotation (A), followed, after a variable interval of 1min, 15min, 1h, 3h, 5,5h and 24h, by a counterclockwise rotation (B). We assessed the level of interference of A on B based on two parameters: the rate of learning and the final level of error reached (asymptote). We found that the rate of learning of B was only slower than A when subjects learned the task 1min apart. No differences were found for the remaining time intervals. In contrast, the asymptotic level of learningreached for both tasks was similar for the 1 min and 15 min intervals, but significantlydecreasedfor B thereafter reaching the best performance levels between the 3h and the 24 h intervals. This pattern of interference followed by facilitation observed over different portions of the learning curve points to the existence of two different neural mechanisms supporting the acquisition of conflicting material: one that depends on a short-term memory of movement direction that decays with time (eg. Taylor and Ivry, 2014), and another that depends on a higher order memory probably acquired through metalearning (e.g. Braun et. al., 2009), which becomes strongeras the memory for A consolidates.