30 research outputs found
Recognizing Speech in a Novel Accent: The Motor Theory of Speech Perception Reframed
The motor theory of speech perception holds that we perceive the speech of
another in terms of a motor representation of that speech. However, when we
have learned to recognize a foreign accent, it seems plausible that recognition
of a word rarely involves reconstruction of the speech gestures of the speaker
rather than the listener. To better assess the motor theory and this
observation, we proceed in three stages. Part 1 places the motor theory of
speech perception in a larger framework based on our earlier models of the
adaptive formation of mirror neurons for grasping, and for viewing extensions
of that mirror system as part of a larger system for neuro-linguistic
processing, augmented by the present consideration of recognizing speech in a
novel accent. Part 2 then offers a novel computational model of how a listener
comes to understand the speech of someone speaking the listener's native
language with a foreign accent. The core tenet of the model is that the
listener uses hypotheses about the word the speaker is currently uttering to
update probabilities linking the sound produced by the speaker to phonemes in
the native language repertoire of the listener. This, on average, improves the
recognition of later words. This model is neutral regarding the nature of the
representations it uses (motor vs. auditory). It serve as a reference point for
the discussion in Part 3, which proposes a dual-stream neuro-linguistic
architecture to revisits claims for and against the motor theory of speech
perception and the relevance of mirror neurons, and extracts some implications
for the reframing of the motor theory
An in vitro whole plant selection system: paraquat tolerant mutants in the fern Ceratopteris
Protocol: genetic transformation of the fern Ceratopteris richardii through microparticle bombardment
BACKGROUND: The inability to genetically transform any fern species has been a major technical barrier to unlocking fern biology. Initial attempts to overcome this limitation were based on transient transformation approaches or achieved very low efficiencies. A highly efficient method of stable transformation was recently reported using the fern Ceratopteris richardii, in which particle bombardment of callus tissue achieved transformation efficiencies of up to 72%. As such, this transformation method represents a highly desirable research tool for groups wishing to undertake fern genetic analysis. RESULTS: We detail an updated and optimized protocol for transformation of C. richardii by particle bombardment, including all necessary ancillary protocols for successful growth and propagation of this species in a laboratory environment. The C. richardii lifecycle comprises separate, free-living gametophyte and sporophyte stages. Callus is induced from the sporophyte apex through growth on cytokinin-containing tissue culture medium and can be maintained indefinitely by sub-culturing. Transgene DNA is introduced into callus cells through particle bombardment, and stable genomic integration events are selected by regeneration and growth of T(0) sporophytes for a period of 8Â weeks on medium containing antibiotics. Selection of T(1) transgenic progeny is accomplished through screening T(1) gametophytes for antibiotic resistance. In many cases sexual reproduction and development of transgenic embryos requires growth and fertilization of gametophytes in the absence of antibiotics, followed by a separate screen for antibiotic resistance in the resultant sporophyte generation. CONCLUSIONS: Genetic transformation of C. richardii using this protocol was found to be robust under a broad range of bombardment and recovery conditions. The successful expansion of the selection toolkit to include a second antibiotic for resistance screening (G-418) and different resistance marker promoters increases the scope of transformations possible using this technique and offers the prospect of more complex analysis, for example the creation of lines carrying more than one transgene. The introduction of a robust and practicable transformation technique is a very important milestone in the field of fern biology, and its successful implementation in C. richardii paves the way for adoption of this species as the first fern genetic model. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13007-015-0080-8) contains supplementary material, which is available to authorized users