Review articleStructure and function of the middle temporal visual area (MT) in the marmoset: Comparisons with the macaque monkey

- The marmoset middle temporal area (MT) is 5-6 times smaller than macaque MT.
- Direction and speed tuning of MT neurons are similar in marmoset and macaque.
- Marmoset MT neurons are tuned to lower spatial frequencies than those in macaques.
- Marmoset MT neurons retain responsiveness following V1 lesions.
- Area MT in marmosets has connections with many higher-order association areas.

Although macaque monkeys have been dominant models in visual neuroscience, recent scientific advances suggest that marmosets provide a valuable alternative in the context of many types of experiments. Here we focus on the middle temporal area (MT), the most extensively studied extrastriate area in primates, and discuss similarities and differences between marmosets and macaques. The basic response properties of MT cells are similar in these species, including direction selectivity, speed tuning, and receptive field centre-surround organization. However, there are differences associated with spatial processing: receptive fields are larger in the marmoset than in the macaque, and MT neurons have preferences for lower spatial frequencies. Comparative analysis of anatomical connections show neural projections from several higher-order association areas to marmoset MT, which seem to be absent or reduced in the macaque. This suggests that cognitive processes could influence the activity of marmoset MT cells more directly. Despite a relative reduction in visual acuity, the present knowledge about the anatomy and physiology of MT in the marmoset suggests that simple low-level visual tasks, which are standard in the literature, are well within the capabilities of marmosets, opening the way for comparative studies of perception and cognition in primate brains of different sizes.