Slow ping over WiFi network

I have two computers on the same WiFi network at home and for some reason from time to time the ping response time pinging my laptop computer from my desktop computer results in rather bad response times of about 100 ms up to 500 ms where the response time normally is approx 1-2 ms. When this happens it's usually fixed by restarting the laptop PC but would still be nice to know what is the actual cause behind this and if there is any way to fix it other than restarting the laptop. Might also mention that the problem is only in one direction, from the desktop computer to the laptop. I've never seen the same problem from the laptop to the desktop PC.

Any good suggestions how I could find out what is causing this?

Try running a constant ping to your router. Do this on both computers.

See this post if you need help doing that:
Computer connected to internet wirelessly but webpages won't load

See the post below the one linked to above. Use a tool like inSSIDer to help determine if you should move to another channel.

Thanks for your tips, I'll try what you suggest and see what it gives.