Formant-Based Recognition of Words and Other Naturalistic Sounds in Rhesus Monkeys

Abstract

In social animals, identifying sounds is critical for communication. In humans, the acoustic parameters involved in speech recognition, such as the formant frequencies derived from the resonance of the supralaryngeal vocal tract, have been well documented. However, how formants contribute to recognizing learned sounds in non-human primates remains unclear. To determine this, we trained two rhesus monkeys to discriminate target and non-target sounds presented in sequences of 1–3 sounds. After training, we performed three experiments: (1) We tested the monkeys’ accuracy and reaction times during the discrimination of various acoustic categories; (2) their ability to discriminate morphing sounds; and (3) their ability to identify sounds consisting of formant 1 (F1), formant 2 (F2), or F1 and F2 (F1F2) pass filters. Our results indicate that macaques can learn diverse sounds and discriminate from morphs and formants F1 and F2, suggesting that information from few acoustic parameters suffice for recognizing complex sounds. We anticipate that future neurophysiological experiments in this paradigm may help elucidate how formants contribute to the recognition of sounds.

Invariant crossmodal equivalence evokes visual imagery from sounds in rhesus monkeys

“…This mechanism could rely on the integration of visual and auditory representations in multisensory areas of the brain (Gaffan and Harrison, 1991; Calvert et al, 2001; Beauchamp et al, 2004; Khandhadia et al, 2021; Diehl et al, 2022; Lemus and Lafuente, 2022), or from connecting neuronal representations of monkey calls at the superior temporal gyrus (STG)(Leaver and Rauschecker, 2010; Tsunada et al, 2011; Bodin and Belin, 2020; Bodin et al, 2021) with unitary activity associated to a monkey face at the superior temporal sulcus (STS)(Tsao et al, 2003; Leopold et al, 2006; Ohayon et al, 2012; Arcaro et al, 2017; Khandhadia et al, 2021). Regardless of NHP being able to discriminate words phonetically(Melchor et al, 2021), it is unclear whether their brains can encode complex sounds like words (Hickok and Poeppel, 2007; Yi et al, 2019; Morán et al, 2021; Stephen et al, 2023) and associate them with visual representations to experience CME.…”