Neurophysiological indices of the effect of cognates on vowel perception in late Spanish-English bilinguals

It is well established that acquiring a second language (L2) later in life results in less accurate production and perception of speech sounds in the L2. Languages like Spanish and English have many common words (cognates) and similar sounds, learning how the combination of cognate status and sound similarity can affect processing and lexical access in an L2 is of interest to educators. In the present study, fifteen monolingual English-speakers and 15 late Spanish-English bilinguals were presented with Spanish-English cognates and non-cognates. Event related potentials (ERP) were used to determine whether late L2-learners had more difficulty discriminating mispronunciations of vowels in English words that have Spanish cognates compared to words that do not have cognates. Behavioral results indicated effects of language background differences, but not cognate status, on participants’ ability to discriminate mispronunciations of English vowels, with bilinguals showing poorer discrimination. ERP results revealed that cognate words facilitated L2 phonological processing as evidenced by a larger frontal positive component (P400) ERP effect, similar in amplitude to the P400 from monolinguals. Results suggest that cognate words facilitate not only vocabulary acquisition, but also speech processing, in adult L2 learners, and, thus, may also be useful as a tool for perceptual learning

T-channel-like pharmacological properties of highvoltage-activated, nifedipine-insensitive Ca(2+) currents inthe rat terminal mesenteric artery

1. Pharmacological properties of nifedipine-insensitive, high voltage-activated Ca(2+) channels in rat mesenteric terminal arteries (NICCs) were investigated and compared with those of α1E and α1G heterologously expressed in BHK and HEK293 cells respectively, using the patch clamp technique. 2. With 10 mM Ba(2+) as the charge carrier, rat NICCs (unitary conductance: 11.5 pS with 110 mM Ba(2+)) are almost identical to those previously identified in a similar region of guinea-pig, such as in current-voltage relationship, voltage dependence of activation and inactivation, and divalent cation permeability. However, these properties are considerably different when compared with α1E and α1G. 3. SNX-482(200 nM and sFTX3.3 (1 μM), in addition to ω-conotoxin GVIA (1 μM) and ω-agatoxin IVA (100 nM), were totally ineffective for rat NICC currents, but significantly suppressed α1E (by 82% at 200 nM; IC(50)=11.1 nM) and α1G (by 20% at 1 μM) channel currents, respectively. A non-specific T-type Ca(2+) channel blocker nimodipine (10 μM) differentially suppressed these three currents (by 40, 3 and 85% for rat NICC, α1E and α1G currents, respectively). 4. Mibefradil, the widely used T-type channel blocker, almost equally inhibited rat NICC and α1G currents in a voltage-dependent fashion with similar IC(50) values (3.5 and 0.3 μM and 2.4 and 0.14 μM at −100 and −60 mV, respectively). Furthermore, other organic T-type channel blockers such as phenytoin, ethosuximide, an arylpiperidine derivative SUN N5030 (IC(50)=0.32 μM at −60 mV for α1G) also exhibited comparable inhibitory efficacies for NICC currents (inhibited by 22% at 100 μM; IC(50)=27.8 mM; IC(50)=0.53 μM, respectively). 5. These results suggest that despite distinctive biophysical properties, the rat NICCs have indistinguishable pharmacological sensitivities to many organic blockers compared with T-type Ca(2+) channels

Involvement of T-type calcium channels in excitatory junction potentials in rat resistance mesenteric arteries

1. We investigated the role of voltage-operated calcium channels in sympathetic transmission and depolarization-induced contractions in the rat mesenteric artery. In particular, we investigated the role of the T-type voltage-operated calcium channels (T-channels) in mediating excitatory junction potentials (EJPs). 2. EJPs were evoked by electrical field stimulation (trains of five stimuli at 0.9 Hz) in small mesenteric arteries. The average resting membrane potential was −59.8±0.5 mV (n=65). Trains of stimuli evoked individual EJPs with the peak EJP of 6±0.2 mV (n=34) occurring with the second stimulus. Trains of EJPs were inhibited 90% by tetrodotoxin (0.1 μM) or by ω-conotoxin GVIA (GVIA, 10 nM) indicating their neural origin. 3. The EJPs were not inhibited by the L-type calcium channel blocker nicardipine at 0.1 μM, a concentration sufficient to abolish the contraction to potassium depolarization. However, mibefradil (3 μM), considered a relatively selective T-channel antagonist, inhibited the EJPs by about 50%. This concentration of mibefradil did not inhibit GVIA-sensitive electrically-evoked twitches of the rat vas deferens. Thus the action of mibefradil in reducing EJPs is unlikely to be due to either inhibition of L- or N-type channels but is probably due to inhibition of T-channels. 4. The finding that Ni(2+) (300 μM), an inhibitor of T-type calcium channels, also reduced EJP amplitude by about 80% but did not block electrically-evoked twitches in the rat vas deferens, further supports an important role of T-channels in mediating small depolarizations associated with the EJPs evoked by sympathetic nerve stimulation