Fig. 3: Older adults show stronger activity in auditory cortex and reduced responses in medial temporal lobe during recognition of musical sequences.

a The results show that the older (n = 39) compared to young (n = 37) adults have significantly stronger activity in the left auditory cortex compared to young adults only when recognising the melodies that were previously memorised. In fact, the top graphs indicate a component occurring about 300 ms after the onset of each tone that was stronger for the older adults for all the tones in the M condition and for all the tones before introducing the variations in the N conditions (i.e. one tone for NT1 and three tones for NT3). In addition, the N100 response to the first tone of the sequences was significantly stronger for old versus young adults in all conditions. b Conversely, older adults showed significantly decreased activity in the hippocampal and inferior temporal regions. This was particularly evident for conditions NT1 and NT3. Here, as highlighted by the red bottom graphs, the older versus young adults exhibited reduced prediction error responses when the sequence was varied. This happened especially for the first tone which introduced the variation in the melodies (i.e. tone two for NT1 and tone four for NT3). Finally, even if to a smaller extent, reduced activity in older adults was also observed for the M condition, where positive components of the neural signals were reduced for all the tones except for the first one. Note that the figure shows the source localised brain activity illustrated for each experimental condition (M, NT1, NT3) in four ROIs (left and right auditory cortex, left and right hippocampal and inferior temporal regions). Grey areas show the statistically significant differences of the brain activity between young (solid red line) and older adults (solid blue, shading indicates standard error in both cases), while red and blue graphs highlight neural components of particular interest. The sketch of the musical tones represents the onset of the sounds forming the musical sequences. The brain templates illustrate the spatial extent of the ROIs.