Thalamostriatal and cerebellothalamic pathways in a songbird, the Bengalese finch

Abstract

Abstract. The thalamostriatal system is a major network in the mammalian brain, originating principally from the intralaminar nuclei of thalamus. Functions of the thalamostriatal system remain unclear, but a subset of these projections provides a pathway through which the cerebellum communicates with the basal ganglia. Both the cerebellum and basal ganglia play crucial roles in motor control. Although songbirds have yielded key insights into the neural basis of vocal learning, it is unknown whether a thalamostriatal system exists in the songbird brain.Thalamic nucleus DLM is an important part of the song system, the network of nuclei required for learning and producing song. DLM receives output from song system basal ganglia nucleus Area X and sits within dorsal thalamus, the proposed avian homolog of the mammalian intralaminar nuclei that also receives projections from the cerebellar nuclei. Using a viral vector that specifically labels presynaptic axon segments, we show in Bengalese finches that dorsal thalamus projects to Area X, the basal ganglia nucleus of the song system, and to surrounding medial striatum. To identify the sources of thalamic input to Area X, we map DLM and cerebellarrecipient dorsal thalamus (DTCbN). Surprisingly, we find both DLM and immediately-adjacent subregions of DTCbN project to Area X. In contrast, a medial-ventral subregion of DTCbN projects to medial striatum outside Area X. Our results suggest the basal ganglia in the song system, like the mammalian basal ganglia, integrate feedback from the thalamic region to which they project as well as thalamic regions that receive cerebellar output.

A histological study of the song system of the carrion crow (Corvus corone)

“…In the mediolateral direction, we observed Uva to be on the same level with Ov and the AFP nucleus DLM (Figure 5). In the zebra finch, Ov and DLM are also found in the same mediolateral plane (http://www.zebrafinchatlas.org, access: February '20, Nicholson et al, 2018), while Uva lies lateral to Ov and therefore differs from the findings in the carrion crow (Karten et al, 2013; http://www.zebrafinchatlas.org, access: December '20).…”

“…In the current study, we tried to identify the DLM based on the zebra finch atlas, since more details about the neuroanatomy are given in this atlas. Additionally, we tried to orientate on other landmarks and studies on other songbirds like the Bengalese finch (Nicholson et al, 2018). The most striking characteristic that helped locating DLM is the huge fiber tract OM (occipitomesencephalic tract) that can be seen ventral to DLM (Karten et al, 2013; Nicholson et al, 2018).…”

“…Additionally, we tried to orientate on other landmarks and studies on other songbirds like the Bengalese finch (Nicholson et al, 2018). The most striking characteristic that helped locating DLM is the huge fiber tract OM (occipitomesencephalic tract) that can be seen ventral to DLM (Karten et al, 2013; Nicholson et al, 2018). Here, we give a first proposal of the stereotactic location of DLM in the carrion crow.…”

“…We think that we could locate the center of DLM quite precisely but to track the exact borders of the nucleus additional research is required. The tracer approach (Nicholson et al, 2018) would be a good option to further investigate the organization of the dorsal thalamic zone and precisely track DLM and its borders in the crow.…”

Unravelling the role of thyroid hormones in seasonal neuroplasticity in European Starlings (Sturnus vulgaris)

“…At the level of the lateral septum Merullo, Cordes et al (2015) showed a positive correlation between neurotensin (a neuropeptide that regulates dopamine activity) expression and both sexually motivated song and non-vocal courtship behaviors in starlings. Whereas in songbirds, only few studies looked at the role of the cerebellum in song behavior through the cerebello-thalamic-basal ganglia pathway (Person, Gale et al 2008, Nicholson, Roberts et al 2018, Pidoux, Le Blanc et al 2018, in humans, the cerebellum is known to be involved in language tasks (lobule VI and crus I/II) and phonological storage during the maintenance of verbal information (VIIb/VIII). Prior lesion study showed that lesioning Area X caused structural remodeling of the cerebello-thalamic-basal ganglia pathway extending into cerebellar lobules VIb and VII (Hamaide, Lukacova et al 2020).…”