A 61-year-old woman with dementia has been left with a broken eye socket following an incident near Bridlington.
Joy Watson, from Manchester, said that a man "thumped her in the face" after she asked him to stop kicking his dog.
She was driving to Bridlington to support friends who were doing the coast to coast cycle ride for charity on Sunday.
The alleged assault took place in the layby on the A164 after she had her breakfast from a roadside cafe.
Mrs Watson, who was diagnosed with onset dementia six-years-ago, said: "The man had a huge Alsatian and was having trouble with it. He then started kicking it.
"I told the man's wife that if he did not stop attacking the dog I would report him and she told me to go away."
The 61-year-old was punched in the face whilst wearing a badge saying: 'I have Alzheimer's please be patient.'
She said that the man punched her in the face and she then hit her head on the concrete ground.
"The couple got back in the car and drove around me not knowing if I was dead or alive," she added.
Joy was taken to Scarborough Hospital following the incident and released on Monday morning.
She is now waiting for surgery to her eye socket whilst resting at home.
Joy decided to dedicate her life to raising awareness of dementia and its impact, and improving everyday life for those with dementia, after being diagnosed at 55-years-old.
Her work was recognised by former Prime Minister David Cameron and she was given a Points of Light award.
Humberside Police has confirmed it is investigating the incident.
A spokesperson said: "The suspect was with another woman who, after the incident, drove off towards Bridlington in a black coloured car, possibly a Hyundai.
"He has been described as in his 60s and wearing fawn and brown clothing."
Anyone with information is asked to call police on 101 quoting reference 16/78234/19.